Detection of electromagnetic radiation using nonlinear materials

ABSTRACT

An apparatus for detecting electromagnetic radiation within a target frequency range is provided. The apparatus includes a substrate and one or more resonator structures disposed on the substrate. The substrate can be a dielectric or semiconductor material. Each of the one or more resonator structures has at least one dimension that is less than the wavelength of target electromagnetic radiation within the target frequency range, and each of the resonator structures includes at least two conductive structures separated by a spacing. Charge carriers are induced in the substrate near the spacing when the resonator structures are exposed to the target electromagnetic radiation. A measure of the change in conductivity of the substrate due to the induced charge carriers provides an indication of the presence of the target electromagnetic radiation.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims priority, under 35 U.S.C. §120, as acontinuation of U.S. non-provisional patent application Ser. No.14/634,307, filed on Feb. 27, 2015, entitled “DETECTION OFELECTROMAGNETIC RADIATION USING NONLINEAR MATERIALS,” which is herebyincorporated herein by reference in its entirety. Ser. No. 14/634,307 inturn claims priority, under 35 U.S.C. §120, as a continuation of U.S.non-provisional patent application Ser. No. 13/933,557, filed on Jul. 2,2013, entitled “DETECTION OF ELECTROMAGNETIC RADIATION USING NONLINEARMATERIALS,” which is hereby incorporated herein by reference in itsentirety. Ser. No. 13/933,557 in turn claims priority to U.S.provisional application Ser. No. 61/667,673, filed Jul. 3, 2012,entitled “DETECTION OF ELECTROMAGNETIC RADIATION USING NONLINEARMATERIALS,” which is hereby incorporated herein by reference in itsentirety.

GOVERNMENT LICENSE RIGHTS

This invention was made with government support under contract no.N00014-09-1-1103 awarded by the Office of Naval Research (ONR). Thegovernment has certain rights in the invention.

BACKGROUND

Technology in the region of the electromagnetic spectrum between theinfrared and microwave ranges holds tremendous promise for advances inapplications such as surveillance and homeland security. Unlike otherregions of the electromagnetic spectrum, development of technologies inthe gigahertz and terahertz frequency ranges has been lacking due tochallenges with generation and detection of electromagnetic radiation atthese frequencies. Light in the gigahertz and terahertz frequency rangesis of great scientific and technological interest because severalelementary physical processes give signatures in this range. Examples ofsuch physical processes include atomic and molecular transitions anddynamics of biological molecules.

Electromagnetic radiation at gigahertz and terahertz frequency rangescan penetrate many packaging materials from a distance and identifymaterial contained within. For example, terahertz frequencies canfacilitate identification of possibly hazardous substances containedwithin packaging materials. Examples of such packaging materials includeshipping containers, storage containers, trucking compartments, etc,that are made of non-conductive materials or sufficiently lowconductivity materials.

There are also sizeable economic and social interests in improvedsecurity screening methods. Government spending on domestic securityalone is estimated at around $75 billion per year. At present, theability to effectively screen harmful substances is somewhat limited. Arapid chemically-specific screening technique would have direct impactson the security, shipping, and travel industries. It can provide for asafer and more efficient environment across many different sectors.

Current technologies generally focus on supplying spatial information.For example, the most frequently used security technologies in airports,federal institutions, and other public arenas, are x-ray scanners andgigahertz scanners. These technologies can show images of concealedhazards (like knives and guns). However, they are able to provide littleto no information about the composition of a potential hazard. Examplesof those hazards include explosives, chemical agents, or biologicalagents. Given that x-rays can be ionizing radiation, there is also thepotential for harm to living tissue.

Spectroscopic imaging in the gigahertz and terahertz frequency rangescan be used to identify both the existence of a concealed hazard and itschemical composition. In addition, it is presently believed thatelectromagnetic radiation in the gigahertz and terahertz frequencyranges do not cause apparent damage to living tissue.

Current terahertz or gigahertz spectroscopic imaging techniques mayrequire time consuming scans to measure spectral and spatialinformation, which can make it impractical for security screening. Also,there are currently very few single element or array detectors for thesefrequency ranges. These include Golay cells, bolometers, andpyroelectric detectors. Each kind of detector has limitations in theirability to be useful both in a wide range of frequencies and as anarray. In addition, these kinds of detectors use a thermal response tomeasure terahertz or gigahertz power. These detectors can be expensive(on the order of $10K to $100K) and slow (response times on the order ofmillisecond). While photocurrent methods have been employed fordetection in the infrared and visible ranges, these photocurrent methodsoften depend on an above bandgap excitation to create electron-holepairs which then generate a measurable change in the current or voltagein the device.

A spectroscopic tool that can be configured to detect and/or quantifyelectromagnetic radiation in the gigahertz and terahertz frequencyranges would be beneficial.

SUMMARY

In view of the foregoing, the Inventors have provided systems, methods,and apparatus that can be used for detecting or otherwise quantifyingelectromagnetic waves at frequencies between microwave frequencies andinfrared frequencies. A local electric field enhancement in thesubstrate of a metamaterial structure is exploited to produce aphoto-induced conductivity response in the substrate of the metamaterialstructure. In an example, the photo-induced conductivity response can becorrelated to the power of the incident electromagnetic radiation. Thephoto-induced conductivity response also can be used to quantify otherproperties of the electromagnetic radiation (including magnitude,spatial profile, polarization, etc.). Any of the apparatus describedherein can be implemented in detectors, image sensors, or other devicesor systems according to the principles described herein.

In a first example aspect, an apparatus is provided for detecting targetelectromagnetic radiation within a target frequency range. The apparatusincludes a substrate that includes a dielectric material or asemiconductor material, and one or more resonator structures disposed onthe substrate. Each of the resonator structures comprising at least twoconductive structures separated by a spacing. The apparatus can beconfigured such that charge carriers are generated in a region of thesubstrate near the spacing based on an enhanced electric field inducedin the spacing by a resonant response of one or more of the resonatorstructures to a presence of the target electromagnetic radiation. Theapparatus can be configured to measure a conductivity based on thegenerated charge carriers. The measure of the conductivity provides anindication of the presence of the target electromagnetic radiation.

In the various examples of any of the apparatus described herein, eachof the one or more resonator structures can have at least one dimensionthat is less than a wavelength of the target electromagnetic radiation.In other examples, each of the one or more resonator structures can haveat least one dimension that is greater than or approximately equal to awavelength of the target electromagnetic radiation.

In the various examples of any of the apparatus described herein, eachof the conductive structures can have at least one dimension that isless than a wavelength of the target electromagnetic radiation. In otherexamples, each of the conductive structures can have at least onedimension that is greater than or approximately equal to a wavelength ofthe target electromagnetic radiation.

In an example of the apparatus, each of the one or more resonatorstructures can include a first conductive structure and a secondconductive structure separated by the spacing, where a portion of thefirst conductive structure and a portion of the second conductivestructure near the spacing are parallel to each other.

In an example of the apparatus, each of the one or more resonatorstructures is formed as a split-ring resonator structure, and eachsplit-ring resonator structure can include at least two spacings formedbetween corresponding pairs of the at least two conductive structures.

In an example of the apparatus, the one or more resonator structures canbe arranged in an alternating interdigitated arrangement such that aportion of a first resonator structure of the one or more resonatorstructures is disposed within a spacing of, and not in physical contactwith, a second resonator structure of the one or more resonatorstructures, where the portion of the first resonator structure isoriented in a direction parallel to a side of the second resonatorstructure neighboring the spacing.

In an example of the apparatus, the one or more resonator structures canbe configured such that the apparatus detects target electromagneticradiation of different polarizations. In an aspect according to thisexample, each of the at least two conductive structures can beconfigured in a wedge morphology. In an aspect according to thisexample, the one or more resonator structures can each include at leastfour conductive structures formed in a cross pattern separated by thespacing.

In an example of the apparatus, the one or more resonator structures caneach include a first conductive structure and a second conductivestructure disposed on the substrate. A surface of the substrate thatincludes the first conductive structure and a second conductivestructure lies in an y-z plane. The first conductive structure and thesecond conductive structure are aligned in a longitudinal antennaarrangement along a z-direction of the substrate, and the spacingseparates an end of the first conductive structure from an end of thesecond conductive structure in the z-direction.

In the various examples of any of the apparatus described herein, thetarget frequency range can range from about 100 GHz to about 100 THz.

In the various examples of any of the apparatus described herein, thewidth of the spacing can be about 1.0 microns, about 1.5 microns, about2.0 microns, or about 2.5 microns. The resonator structure can have alateral dimension ranging from about 3.0 μm to about 3.0 mm.

In the various examples of any of the apparatus described herein, theconductive structure can include a metal or a conductive metal oxide.For example, the conductive structure can include gold, platinum copper,tantalum, tin, tungsten, titanium, tungsten, cobalt, chromium, silver,nickel or aluminum, or any combination thereof.

In the various examples of any of the apparatus described herein, thesubstrate can include a dielectric material. In an example, thedielectric material can include silicon, germanium, or a transitionmetal. In an example, the dielectric material can include a transitionmetal, where the transition metal is Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Ru,Hf, Ta, Zr, or any combination thereof. In an example, the dielectricmaterial can include VO2 or (V1-xTix)2O3. in another example, thedielectric material can include an oxide, a phosphate, or a silicate, ofa transition metal.

In the various examples of any of the apparatus described herein, thesubstrate can include a semiconductor material. The semiconductormaterial can include silicon, germanium, or a III-V semiconductor. In anexample, the semiconductor material can include GaAs, InAs, InGaAs, InP,AlSb or InSb.

In the various examples of any of the apparatus described herein, themeasure of the conductivity is a voltage measurement or a currentmeasurement. In an example, the measure of the conductivity provides anindication of the presence of the target electromagnetic radiation ifthe measure of the conductivity exceeds a pre-determined thresholdvalue. In an example, the measure of the conductivity provides anindication of a magnitude, a polarization, or a spatial profile of thetarget electromagnetic radiation.

In a second example aspect, an apparatus for detecting targetelectromagnetic radiation within a target frequency range is providedthat includes a substrate comprising a dielectric material or asemiconductor material, and a first conductive structure and a secondconductive structure disposed on the substrate. A spacing separates afirst end of the first conductive structure from a first end of thesecond conductive structure. The first conductive structure and thesecond conductive structure are configured such that the apparatusdetects the target electromagnetic radiation of different polarizations.In an example according to this aspect, the first conductive structureand the second conductive structure can each be configured in a wedgemorphology. In another example according to this aspect, the apparatuscan further include a third conductive structure and a fourth conductivestructure disposed on the substrate, where the first conductivestructure, the second conductive structure, the third conductivestructure, and the fourth conductive structure are formed in a crosspattern separated by the spacing. In another example according to thisaspect, the first end of the first conductive structure and the firstend of the second conductive structure near the spacing can each beconfigured in a dual prong morphology. In another example according tothis aspect, the apparatus can further include a first electrodedisposed on the substrate and in electrical communication with an end ofthe first conductive structure at a position away from the spacing, anda second electrode disposed on the substrate and in electricalcommunication with an end of the second conductive structure at aposition away from the spacing. The apparatus can be configured suchthat charge carriers are generated in a region of the substrate near thespacing based on an enhanced electric field induced in the spacing by aresonant response of the first conductive structure and the secondconductive structure to a presence of the target electromagneticradiation having the different polarizations, where the apparatus isconfigured to measure, using the first electrode and the secondelectrode, a conductivity based on the generated charge carriers as anindication of the presence of the target electromagnetic radiation.

A detector, image sensor, or other device or system according toprinciples herein can include a plurality of any of the apparatusdescribed herein. The conductive structures can be disposed on a firstsurface of the substrate, and the substrate can include a chargeseparation region. The apparatus can be illuminated by targetelectromagnetic radiation at a second surface of the substrate oppositeto the first surface, and the charge carriers that are generated areelectron-hole pairs. The thickness of the substrate is configured suchthat the electron-hole pairs formed in the charge separation region whenthe image sensor is illuminated by the target electromagnetic radiationare measured to provide an indication of a presence of the targetelectromagnetic radiation.

In a third example aspect, an apparatus for detecting targetelectromagnetic radiation within a target frequency range is providedthat includes a substrate comprising a dielectric material or asemiconductor material, and a first resonator structure and a couplingdipole structure disposed on the substrate. A portion of the firstcoupling structure is disposed within a spacing of the first resonatorstructure, where the first coupling structure is not in physical contactwith the first resonator structure. In an example according to thisaspect, the apparatus can be configured such that charge carriers aregenerated in a region of the substrate near the spacing based on anenhanced electric field induced in the spacing by a resonant response ofthe resonator structure to a presence of the target electromagneticradiation having the different polarizations. The apparatus can beconfigured to measure the conductivity based on the generated chargecarriers as an indication of a presence of the target electromagneticradiation, and the measure of the conductivity can be a voltagemeasurement or a current measurement. In an example according to thisaspect, the measure of the conductivity provides an indication of thepresence of the target electromagnetic radiation if the measure of theconductivity exceeds a pre-determined threshold value. In an exampleaccording to this aspect, the measure of the conductivity provides anindication of a magnitude, a polarization, or a spatial profile of thetarget electromagnetic radiation.

Another example detector, image sensor, or other device or systemaccording to principles herein can include a plurality of any of theapparatus according to this aspect. A plurality of the first resonatorstructures and the first dipole structures can be disposed on a firstsurface of the substrate; where the substrate can include a chargeseparation region. The apparatus can be illuminated by targetelectromagnetic radiation at a second surface of the substrate oppositeto the first surface, and the charge carriers that are generated in thesubstrate by a resonant response of the plurality of the first resonatorstructures and the first dipole structures to a presence of the targetelectromagnetic radiation. The thickness of the substrate is configuredsuch that the electron-hole pairs formed in the charge separation regionwhen the image sensor is illuminated by target electromagnetic radiationare measured to provide an indication of the presence of the targetelectromagnetic radiation. In an example, the charge separation regioncan be a depletion region at an interface within the substrate. In anexample, the substrate ca be back-thinned, where the back-thinning ofthe substrate causes the electron-hole pairs generated by the targetelectromagnetic radiation to be formed in the charge separation region,and where a potential in the charge separation region separates theelectron-hole pairs, thereby facilitating measurement of the chargecarriers to provide an indication of the presence of the targetelectromagnetic radiation.

In a fourth example aspect, an apparatus for detecting electromagneticradiation within a target frequency range is provided that includes asubstrate comprising a dielectric material or a semiconductor material,where a surface of the substrate lies in an y-z plane. A firstconductive structure and a second conductive structure are disposed onthe substrate, where the first conductive structure and the secondconductive structure are aligned in a longitudinal antenna arrangementalong a z-direction of the substrate. A spacing separates an end of thefirst conductive structure from an end of the second conductivestructure in the z-direction, where the target electromagnetic radiationis of a frequency within the target frequency range. The apparatus alsoincludes a first electrode and a second electrode disposed on thesubstrate, where the first electrode is in electrical communication withan end of the first conductive structure at a position away from thespacing, and where the second electrode is in electrical communicationwith an end of the second conductive structure at a position away fromthe spacing. An example apparatus according to this aspect can furtherinclude at one additional conductive structure disposed on thesubstrate, where the at least one additional conductive structure ispositioned between and spaced apart from the first conductive structureand the second conductive structure in the longitudinal antennaarrangement along the z-direction of the substrate, and where each theat least one additional conductive structure is spaced apart from theother of the at least one additional conductive structure in thelongitudinal antenna arrangement.

Another example detector, image sensor, or other device or systemaccording to principles herein can include a plurality of any of theapparatus described herein. The apparatus can be configured forgenerating a resonant response with alternating charge accumulation inresponse to a presence of the target electromagnetic radiation, wherethe detector detects an amplitude of the target electromagneticradiation based on a measurement of an amount the charge accumulation.In an example, the detector, image sensor, or other device or system canbe used to detect a spatial profile of the target electromagneticradiation based on the measurement.

In a fifth example aspect, an apparatus for detecting electromagneticradiation within a target frequency range includes a substrate thatincludes a dielectric material or a semiconductor material, where asurface of the substrate lies in an y-z plane, at least two conductivestructures disposed on the substrate, and at least two electrodes. Theat least two conductive structures are aligned in a longitudinal antennaarrangement along a z-direction of the substrate, where a spacingseparates an end of one of the at least two conductive structures fromanother of the at least two conductive structures in the z-direction,and where the target electromagnetic radiation is of a frequency withinthe target frequency range. Each of the at least two electrodes is inelectrical communication with an end of a respective one of the at leasttwo conductive structures at a position away from the spacing. Anexample apparatus according to this aspect can further include at leastfour conductive structures disposed on the substrate and at least fourelectrodes. Each conductive structure of a first pair of the at leastfour conductive structures can have a first length that targetselectromagnetic radiation of a first frequency within the targetfrequency range, where the first pair of the at least four conductivestructures are aligned and spaced apart in a longitudinal antennaarrangement along the z-direction of the substrate. Each of a first pairof the at least four electrodes is in electrical communication with anend of a respective one of the first pair of the at least fourconductive structures at a position away from the spacing. Eachconductive structure of a second pair of the at least four conductivestructures can have a second length that is less than the first length,where the second pair of the at least four conductive structures targetselectromagnetic radiation of a second frequency within the targetfrequency range. The second pair of the at least four conductivestructures can be aligned in a longitudinal antenna arrangement alongthe z-direction of the substrate. Each of a second pair of the at leastfour electrodes is in electrical communication with an end of arespective one of the second pair of the at least four conductivestructures at a position away from the spacing. The second frequency isgreater than the first frequency.

Another example detector, image sensor, or other device or systemaccording to principles herein can include a plurality of any of theapparatus according to this aspect. The apparatus can be configured forgenerating a resonant response with alternating charge accumulation inresponse to a presence of target electromagnetic radiation. The exampledetector, image sensor, or other device or system can be used to detectan amplitude of target electromagnetic radiation based on a measurementof an amount the charge accumulation. The example detector, imagesensor, or other device or system can be used to detect a spatialprofile of the target electromagnetic radiation based on themeasurement.

Another example detector, image sensor, or other device or systemaccording to principles herein can include a plurality of sensorelements, where each sensor element can include a substrate thatincludes a semiconductor material or a dielectric material, and one ormore resonator structures disposed on a surface of the substrate. Eachof the resonator structures can include at least two conductivestructures separated by a spacing, where the substrate can include adepletion region. The sensor elements can be configured such that chargecarriers are generated in a region of the substrate near the spacingbased on an enhanced electric field induced in the spacing by a resonantresponse of one or more of the resonator structures to a presence oftarget electromagnetic radiation. The thickness of the substrate can beconfigured such that charge carriers are generated in the depletionregion when the image sensor is illuminated by the targetelectromagnetic radiation, where the image sensor is configured tomeasure a conductivity based on the generated charge carriers as anindication of the presence of the target electromagnetic radiation. Inan example, each of the one or more resonator structures can have atleast one dimension that is less than a wavelength of the targetelectromagnetic radiation. In another example, each of the one or moreresonator structures can have at least one dimension that is greaterthan or approximately equal to a wavelength of the targetelectromagnetic radiation.

Another example detector, image sensor, or other device or systemaccording to principles herein can include a plurality of sensorelements, where each sensor elements can include a substrate and one ormore resonator structures disposed over a first surface of thesubstrate. Each of the resonator structures can include at least twoconductive structures separated by a spacing. The substrate can includea depletion region. The sensor elements can be configured such thatcharge carriers are generated in a region of the substrate near thespacing based on an enhanced electric field induced in the spacing by aresonant response of one or more of the resonator structures to apresence of target electromagnetic radiation. The thickness of thesubstrate can be configured such that charge carriers are generated inthe depletion region when the image sensor is illuminated by the targetelectromagnetic radiation. The example detector, image sensor, or otherdevice or system can be configured to measure a conductivity based onthe generated charge carriers as an indication of the presence of thetarget electromagnetic radiation. In an example, each of the one or moreresonator structures can have at least one dimension that is less than awavelength of the target electromagnetic radiation. In an example, eachof the one or more resonator structures can have at least one dimensionthat is greater than or approximately equal to a wavelength of thetarget electromagnetic radiation.

In example detectors, image sensors, or other devices or systemsaccording to principles herein, each of the one or more resonatorstructures can include a first conductive structure and a secondconductive structure separated by the spacing, where a portion of thefirst conductive structure and a portion of the second conductivestructure near the spacing are parallel to each other.

In other example detectors, image sensors, or other devices or systemsaccording to principles herein, each of the one or more resonatorstructures can be formed as a split-ring resonator structure, where eachsplit-ring resonator structure includes at least two spacings formedbetween corresponding pairs of the at least two conductive structures.

In other example detectors, image sensors, or other devices or systemsaccording to principles herein, the one or more resonator structures canbe arranged in an alternating interdigitated arrangement such that aportion of a first resonator structure of the one or more resonatorstructures is disposed within a spacing of, and not in physical contactwith, a second resonator structure of the one or more resonatorstructures, where the portion of the first resonator structure isoriented in a direction parallel to a side of the second resonatorstructure neighboring the spacing.

In other example detectors, image sensors, or other devices or systemsaccording to principles herein, the one or more resonator structures canbe configured such that the apparatus detects target electromagneticradiation of different polarizations. In an example, each of the atleast two conductive structures is configured in a wedge morphology. Inan example, the one or more resonator structures each can include atleast four conductive structures formed in a cross pattern separated bythe spacing.

In other example detectors, image sensors, or other devices or systemsaccording to principles herein, the one or more resonator structureseach can include a first conductive structure and a second conductivestructure disposed on the substrate. A surface of the substrate thatincludes the first conductive structure and a second conductivestructure lies in an y-z plane, where the first conductive structure andthe second conductive structure are aligned in a longitudinal antennaarrangement along a z-direction of the substrate and the spacingseparates an end of the first conductive structure from an end of thesecond conductive structure in the z-direction.

In a fifth example aspect, an apparatus is provided for detecting targetelectromagnetic radiation within a target frequency range that includesa substrate including a dielectric material or a semiconductor material,and a first resonator structure and a coupling dipole structure disposedon the substrate. A portion of the first coupling structure is disposedwithin a spacing of the first resonator structure, where the firstcoupling structure is not in physical contact with the first resonatorstructure. In an example, each of the first resonator structure and thefirst coupling structure is of a size less than a wavelength of thetarget electromagnetic radiation. In an example, each of the firstresonator structure and the first coupling structure is of a sizegreater than or approximately equal to a wavelength of the targetelectromagnetic radiation. In an example, the portion of the firstcoupling structure disposed within the spacing is oriented in adirection perpendicular to a portion of the resonator structureneighboring the spacing.

Methods for detecting a polarization of target electromagnetic radiationwithin a target frequency range are also provided.

In an example aspect, a method can include exposing a plurality ofsensor elements of an image sensor to an incident beam ofelectromagnetic radiation, and measuring a change in conductivity of thesubstrate of the one or more rotated sensor elements based on thegenerated charge carriers. Each sensor element can include a substrateincluding a dielectric material or a semiconductor material, and one ormore resonator structures disposed on the substrate, each of theresonator structures including at least two conductive structuresseparated by a spacing. Each sensor element can be configured such thatcharge carriers are generated in a region of the substrate near thespacing based on an enhanced electric field induced in the spacing by aresonant response of one or more of the resonator structures to apresence of the target electromagnetic radiation. The measure of thechange in conductivity can be used to provide an indication of thepresence of the target electromagnetic radiation in the incident beam ofelectromagnetic radiation. In an example, each of the one or moreresonator structures can have at least one dimension that is less than awavelength of the target electromagnetic radiation. In an example, eachof the one or more resonator structures can have at least one dimensionthat is greater than or approximately equal to a wavelength of thetarget electromagnetic radiation. The method of claim 102, furthercomprising rotating one or more sensor elements of the plurality ofsensor elements, where the measure of the change in conductivity of thesubstrate of the one or more rotated sensor elements provides anindication of the polarization of the target electromagnetic radiation.

In an example of the method, the measure of the change in theconductivity can be used to provide the indication of the polarizationof the target electromagnetic radiation if it exceeds a pre-determinedthreshold conductivity value.

In another example of the method, the one or more of the resonatorstructures can have a wedge morphology or a cross pattern.

In an example, a detector, image sensor, or other device or systemaccording to principles herein can include an array including aplurality of sensor elements for detecting target electromagneticradiation within a target frequency range. Each sensor element caninclude a substrate including a dielectric material or a semiconductormaterial and one or more resonator structures disposed on the substrate.Each of the resonator structures can include at least two conductivestructures separated by a spacing, where the refractive index of thesubstrate of at least one of the sensor elements of the array differsfrom the refractive index of the substrate of other sensor elements ofthe array. The apparatus can be configured such that charge carriers aregenerated in a region of the substrate near the spacing based on anenhanced electric field induced in the spacing by a resonant response ofone or more of the resonator structures to a presence of the targetelectromagnetic radiation. The apparatus can be configured to measure aconductivity based on the generated charge carriers. The measure of theconductivity can be used to provide an indication of the presence of thetarget electromagnetic radiation. In an example, each of the one or moreresonator structures can have at least one dimension that is less than awavelength of the target electromagnetic radiation. In an example, eachof the one or more resonator structures can have at least one dimensionthat is greater than or approximately equal to a wavelength of thetarget electromagnetic radiation.

In an example, a detector, image sensor, or other device or systemaccording to principles herein can include an array including aplurality of sensor elements for detecting target electromagneticradiation within a target frequency range. Each sensor element caninclude a substrate including a dielectric material or a semiconductormaterial, and one or more resonator structures disposed on thesubstrate. Each of the resonator structures can include at least twoconductive structures separated by a spacing. The dimensions of the oneor more resonator structures of at least one of the sensor elements ofthe array can differ from the dimensions of the one or more resonatorstructures of other sensor elements of the array. The apparatus can beconfigured such that charge carriers are generated in a region of thesubstrate near the spacing based on an enhanced electric field inducedin the spacing by a resonant response of one or more of the resonatorstructures to a presence of the target electromagnetic radiation. Theapparatus can be configured to measure a conductivity based on thegenerated charge carriers. The measure of the conductivity can be usedto provide an indication of the presence of the target electromagneticradiation. In an example, each of the one or more resonator structurescan have at least one dimension that is less than a wavelength of thetarget electromagnetic radiation. In an example, each of the one or moreresonator structures can have at least one dimension that is greaterthan or approximately equal to a wavelength of the targetelectromagnetic radiation.

It should be appreciated that all combinations of the foregoing conceptsand additional concepts discussed in greater detail below (provided suchconcepts are not mutually inconsistent) are contemplated as being partof the inventive subject matter disclosed herein. In particular, allcombinations of claimed subject matter appearing at the end of thisdisclosure are contemplated as being part of the inventive subjectmatter disclosed herein. It should also be appreciated that terminologyexplicitly employed herein that also may appear in any disclosureincorporated by reference should be accorded a meaning most consistentwith the particular concepts disclosed herein.

BRIEF DESCRIPTION OF THE DRAWINGS

The skilled artisan will understand that the drawings primarily are forillustrative purposes and are not intended to limit the scope of theinventive subject matter described herein. The drawings are notnecessarily to scale; in some instances, various aspects of theinventive subject matter disclosed herein may be shown exaggerated orenlarged in the drawings to facilitate an understanding of differentfeatures. In the drawings, like reference characters generally refer tolike features (e.g., functionally similar and/or structurally similarelements).

FIG. 1 illustrates the electromagnetic spectrum from the microwave andmillimeter wave region to x-ray frequencies.

FIG. 2A shows an example detector element, according to principles ofthe present disclosure.

FIG. 2B shows a magnified view of a portion of the example detectorelement of FIG. 2A, according to principles of the present disclosure.

FIG. 3 shows example arrays of sensor elements, according to principlesof the present disclosure.

FIG. 4 shows another example detector element, according to principlesof the present disclosure.

FIG. 5 shows a portion of an example array of resonator structurescoupled with coupling structures, according to principles of the presentdisclosure.

FIG. 6 shows another example of an array of the resonator structurescoupled with coupling structures shown in FIG. 5, according toprinciples of the present disclosure.

FIGS. 7A and 7B show example arrays of detector elements withinterdigitated resonator structures, according to principles of thepresent disclosure.

FIG. 8 show another example detector element, according to principles ofthe present disclosure.

FIG. 9A shows an example detector element with an antenna arrangement ofconductive structures, according to principles of the presentdisclosure.

FIG. 9B shows another example detector element with an antennaarrangement of conductive structures, according to principles of thepresent disclosure.

FIG. 10A shows another example detector element with an antennaarrangement of conductive structures, according to principles of thepresent disclosure.

FIG. 10B shows another example detector element with an antennaarrangement of conductive structures, according to principles of thepresent disclosure.

FIG. 11 shows an example detector element formed from conductivestructures in an antenna arrangement, according to principles of thepresent disclosure.

FIG. 12 shows another example of detector elements formed fromconductive structures in an antenna arrangement, according to principlesof the present disclosure.

FIG. 13A shows another example of detector elements formed from anarrangement of resonator structures, according to principles of thepresent disclosure.

FIG. 13B shows a plot of frequencies of electromagnetic radiation thatcan be detected using the detector element of FIG. 13A, according toprinciples of the present disclosure.

FIG. 14A shows an example detector formed from an arrangement ofresonator structures, according to principles of the present disclosure.

FIG. 14B shows an example use of the resonator structures of FIG. 14A aspart of a detector or image sensor, according to principles of thepresent disclosure.

FIG. 15A shows an array of example split-ring resonator structures,according to principles of the present disclosure.

FIG. 15B shows a magnified view of one of the example split-ringresonator structures in the array of FIG. 15A, according to principlesof the present disclosure.

FIG. 16 shows an example front-illumination sensor element, according toprinciples of the present disclosure.

FIGS. 17A-B show example back-illumination sensor elements, according toprinciples of the present disclosure.

FIGS. 18A-18D illustrates a schematic of absorption of photons in asensor element, according to principles of the present disclosure.

FIG. 19 shows example arrays of sensor elements formed as pixels,according to principles of the present disclosure.

FIG. 20 shows a block diagram of an example CMOS image sensor thatincludes a pixel array, according to principles of the presentdisclosure.

FIG. 21 shows an example processing system that includes an imagesensor, according to principles of the present disclosure.

DETAILED DESCRIPTION

Following below are more detailed descriptions of various conceptsrelated to, and embodiments of, inventive methods, apparatus, andsystems for detecting or otherwise quantifying electromagnetic radiationof frequency on the order of gigahertz and/or terahertz frequencies, anddetectors, image sensors, and other devices based thereon. It should beappreciated that various concepts introduced above and discussed ingreater detail below may be implemented in any of numerous ways, as thedisclosed concepts are not limited to any particular manner ofimplementation. Examples of specific implementations and applicationsare provided primarily for illustrative purposes.

As used herein, the term “includes” means includes but is not limitedto, the term “including” means including but not limited to. The term“based on” means based at least in part on.

With respect to substrates or other surfaces described herein inconnection with various examples of the principles herein, anyreferences to “top” surface and “bottom” surface are used primarily toindicate relative position, alignment and/or orientation of variouselements/components with respect to the substrate and each other, andthese terms do not necessarily indicate any particular frame ofreference (e.g., a gravitational frame of reference). Thus, reference toa “bottom surface of a substrate” does not necessarily require that theindicated surface be facing a ground surface. Similarly, terms such as“over,” “under,” “above,” “beneath” and the like do not necessarilyindicate any particular frame of reference, such as a gravitationalframe of reference, but rather are used primarily to indicate relativeposition, alignment and/or orientation of various elements/componentswith respect to the substrate (or other surface) and each other. Theterms “disposed on” and “disposed over” encompass the meaning of“embedded in,” including “partially embedded in.” In addition, referenceto feature A being “disposed on” or “disposed over” feature Bencompasses examples where feature A is in contact with feature B, aswell as examples where other layers and/or other components arepositioned between feature A and feature B.

Systems, apparatus and methods described herein can be used fordetecting electromagnetic waves at frequencies betweenmillimeter/microwave frequencies and infrared (IR) frequencies. Forexample, systems, apparatus and methods described herein can be used fordetecting electromagnetic waves at frequencies in the gigahertz andterahertz frequency ranges. As a non-limiting example, systems,apparatus and methods described herein can be used for detecting targetelectromagnetic waves at frequencies ranging from about 100 GHz to about100 THz. This region is referred to collectively herein as the“detection range” of the electromagnetic spectrum. An example of thedetection range is illustrated in the non-limiting exampleelectromagnetic spectrum of FIG. 1. In other examples, the detectionrange may encompass frequencies somewhat lower than about 100 GHz and/orfrequencies somewhat higher than about 100 THz. Electromagneticradiation with frequencies in the detection range have wavelengths in avacuum that range from about 3.0 μm to about 3.0 mm.

A system, apparatus and method herein exploit the measurable changes inthe conductivity (i.e., current and/or voltage) in a device according toprinciples herein for detecting or otherwise quantifying electromagneticradiation at frequencies in the detection range. In an example, thedetection is facilitated by exploiting below bandgap excitation atterahertz frequencies or above bandgap excitation at frequencies in theIR.

An example apparatus, detector, image sensor, or other device or systemaccording to principles herein are comprised of one or more detectorelements. Each detector element is based on materials that exhibitnon-linear excitations in the gigahertz and terahertz frequency ranges.In an example, the detector elements can be based on metamaterials thatare configured to resonate with electromagnetic radiation in thegigahertz and terahertz frequency ranges. In a non-limiting example, themetamaterial is formed from one or more resonator structures disposed ona substrate. The detector elements herein exploit the Inventors'observation that light at frequencies in the detection range can be usedto modify the properties of metamaterial-based devices according to theprinciples described herein.

In an example, an apparatus, detector, image sensor, or other device orsystem according to principles herein can be used to detect or otherwisequantify electromagnetic radiation at a frequency in the detection rangebased on local changes in the conductivity induced in the substrate ofthe metamaterial structures according to principles herein. The localchange in conductivity can be induced when the metamaterial structuresresonate with electromagnetic radiation in the gigahertz and terahertzfrequency ranges. In an example, the substrate of the metamaterial canbe a dielectric, and the local change in the conductivity can based onan electric field-induced insulator-to-metal phase transition in thedielectric. As a non-limiting example, the dielectric material can be anoxide, including an oxide of silicon or a transition metal oxide, suchas but not limited to VO₂. In an example, the substrate of themetamaterial can be a semiconductor, and the local change in theconductivity can based on impact ionization in the semiconductor. Asnon-limiting examples, a lower bandgap semiconductor, such as but notlimited to indium antimonide (InSb) or indium arsenide (InAs), can beused to generate charge carriers (e.g., electron-hole pairs) accordingto the principles described herein. In other non-limiting examples, ahigher bandgap semiconductor, such as but not limited to indiumphosphide (InP), gallium arsenide (GaAs) and aluminum antimonide (AlSb),can be used to generate charge carriers according to the principlesdescribed herein. A substrate of a metamaterial structure according tothe principles herein, including a semiconductor substrate, can beundoped or can be doped with n-type or p-type dopants such that itsconductivity varies from more insulating (e.g., about 10⁷/cm³ carrierdensity or less) to more conductive (e.g., about 10¹⁶/cm³ carrierdensity or more), including values of carrier density within the rangefrom about 10⁷/cm³ to about 10¹⁶/cm³. As a non-limiting example, thesubstrate can be n-type doped GaAs (e.g., GaAs doped with Si). Themetamaterial structures according to principles herein can be used tofacilitate sub-wavelength field enhancement that drive the nonlinearresponse locally.

A resonator structure according to principles herein is formed from atleast two conductive structures separated by a spacing. While ametamaterial structure herein is described as including one or moreresonator structure disposed on a surface of a substrate, themetamaterial can include other components, including one or morecoupling structures and/or other active components.

When a resonator structure according to principles herein is irradiatedby electromagnetic radiation of a frequency in the detection range, thelocal electric field enhancement in the vicinity of the at least onespacing in the resonator structure can induce a local change in theconductivity of the substrate in the vicinity of the spacing. In effect,the resonator structures according to the principles herein areconfigured to act as local resonant field concentrators. The enhancedelectric field inside the spacing (approximated as a capacitive gap) canbe enhanced by an order of magnitude or more. In some exampleconfigurations, the resonator structures can be modeled asinductor-capacitor (LC) circuits with the spacing being approximated asthe capacitive gap. The substrate performs the dual functions offacilitating the electric field enhancement that drives the nonlinearresponse locally and facilitating global sensitivity to the localizedconductivity change that enables measurement. As a non-limiting example,the local conductivity can change by at least an order of magnitude ormore. For example, in a metamaterial based on a VO₂ substrate, the localelectric field enhancement can induce a change in the local conductivityby about two orders of magnitude or more at the spacing of the resonatorstructure. For an example metamaterial based on a semiconductorsubstrate, such as but not limited to a silicon, GaAs, InGaAs, InAs,InP, or InSb substrate, the conductivity change can be up to about tenorders of magnitude or more at the spacing of the resonator structure.

The response time of the substrate to the local electric fieldenhancement, whether for an insulator-to-metal phase transition in adielectric substrate or impact ionization in a semiconductor substrate,can be sufficiently long enough such that the transient large change inphoto-conductivity can be measured or otherwise quantified. As anon-limiting example, for a dielectric substrate of VO₂, the responsetimes can be over 100 ps to possibly several nanosecond long. As anothernon-limiting example, for a semiconductor substrate of InSb, theresponse times also can be in excess of 100 ps to possibly severalnanoseconds long. In an example, the change in photo-inducedconductivity in the resonator structure may be measured or otherwisequantified using electrodes in electrical communication with theresonator structure. In another example, the photo-induced conductivityin the resonator structure may be measured or otherwise quantified usingintegrated circuitry coupled to the substrate on which the resonatorstructure is disposed.

According to an example apparatus, a detector, image sensor, or otherdevice or system according to principles herein can include at least onedetector element that is configured such that charge carriers aregenerated in the region of the substrate near the spacing between theconductive structures of the resonator structure. The charge carrierscan be generated based on an enhanced electric field induced in thespacing by a resonant response of the one or more resonator structuresto the presence of target electromagnetic radiation. The apparatus canbe configured to measure a change in conductivity based on the generatedcharge carriers. In an example, the change in conductivity lastssufficiently long that it can be measured. For example, such ameasurement can be made with high bandwidth amplifier electronics. Themeasure of the current can be used to provide an indication of thepresence of the target electromagnetic radiation.

The change in conductivity of the detector element can be measured usingelectrodes in electrical communication with (or otherwise electricallycoupled to) at least one of the resonator structures, or using readoutcircuitry associated with the detector element. The measuredconductivity in the presence of the target electromagnetic radiation canbe compared to the measured conductivity in the absence of the targetelectromagnetic radiation. A change in the measured conductivity can beindicative of the presence of the target electromagnetic radiation, orotherwise quantify a property of the target electromagnetic radiation(including magnitude, spatial profile, polarization, etc.). In anexample, the change in conductivity can be measured using high bandwidthamplifier electronics.

In some non-limiting examples, at least one feature size or dimension ofthe resonator structures disposed on the substrate can be configured tobe smaller than the wavelength of the target electromagnetic radiationor the half-wavelength of the target electromagnetic radiation.

In some non-limiting examples, at least one feature size or dimensioncan be greater than or approximately equal to the half-wavelength of thetarget electromagnetic radiation. A detector, image sensor, or otherdevice or system that includes resonator structures with feature sizesgreater than or approximately equal to the half-wavelength of the targetelectromagnetic radiation can be used for resonating higher order modesof the resonator structure with the target electromagnetic radiation.

In some examples, a resonator structure can be modeled as an individualinductor-capacitor (LC) circuit with resonant frequency, ω₀˜(LC)^(−1/2).The resonator structure can be modeled as a distributed inductance (L)and a distributed capacitance (C) arising from charge build-up at thespacing. The materials of the conductive structures and the dimensionsof the resonator structures set the parameters L and C, and determinethe resonant frequency of the metamaterial structure, i.e., the targetelectromagnetic frequency or range of frequencies that resonate with themetamaterial structure.

In an example, the target electromagnetic frequency (or range offrequencies) that resonates with the metamaterial structures accordingto principles herein can be changed (i.e., tuned) by changing thematerials of the conductive structures that form the resonatorstructures.

In another example, the target electromagnetic frequency (or range offrequencies) that resonates with the metamaterial structures accordingto principles herein can be changed (i.e., tuned) by changing thedimensions of the conductive structures that form the resonatorstructures.

In another example, the resonance of the metamaterial structure can bescale-invariant for a given choice of materials of the conductivestructures and morphology of the resonator structures. That is, thetarget electromagnetic frequency (or range of frequencies) thatresonates with the metamaterial structure according to principles hereincan be changed (i.e., tuned) by scaling-up (for lower resonancefrequencies) or scaling-down (for higher resonance frequencies) thedimensions of the one or more resonator structures. In various examples,the metamaterial structures according to the principles herein can beconfigured through up-conversion or down-conversion to resonate withfrequencies outside the detection range, i.e., from visible wavelengthsthrough millimeter wavelengths. In an example according to thisprinciple, an array of detector elements that include resonatorstructures at different scales can be used to detect or otherwisequantify electromagnetic radiation at differing frequencies. In anexample according to this principle, the array of detector elements canbe spatially arranged such that differing regions of the array resonatewith electromagnetic radiation of differing frequencies.

The metamaterial-based detector elements in the detection rangedescribed herein have direct application in the field of spectroscopy inthe gigahertz and terahertz frequency ranges. The detector elementsherein and devices that include them can facilitate reducing theresponse time as compared to devices that rely on a thermal response ofa material for detection. The detectors herein also can be moresensitive than devices that rely on a thermal response for detection.The principle of operation of the detectors herein lends itself to arraydetection and could provide a better way to image the spatial profile ofelectromagnetic radiation in the detection range.

Image sensors may be formed based on any of the detector elementsaccording to the principles described herein. The image sensors can beconfigured as back-thinned devices. In an example, a back-thinned devicethat includes one or more detector elements according to principlesdescribed herein can be sensitive to longer wavelengths of light. Inoperation of a back-thinned device, the concentration of the THz to IRfield in a portion of the detector element liberates electrons near asurface of the back-thinned substrate. Where the back-thinned deviceincludes a depletion region near the substrate surface, electron-holepairs formed in the depletion region can be collected efficiently. As aresult, the back-thinned devices provided herein can be highlyefficient.

A detector or other device that includes a detector element according toany of the examples described herein can be both fast and sensitive. Thedetection is based on the generation of charge carriers according toprinciples of any of the examples herein and their subsequentrelaxation, which can be on the order of nanosecond timescales.Fabrication costs for the metamaterial structures herein may be lowsince lower cost methods may be used, including photolithographicmethods. A detector according to principles herein could possiblyperform over an order of magnitude faster than a detector based on athermal response.

Detector Elements and Sensor Elements

An apparatus, detector, image sensor, or other device or systemaccording to principles herein is based on an assembly of one or moredetector elements. Each detector element includes a substrate having atleast one resonator structure disposed in its surface. In an example,the detector elements can be configured as an array of resonatorstructures disposed on a surface of a substrate. Non-limiting examplesof applicable resonator structures or arrays that include resonatorstructures according to principles herein are shown in FIGS. 2A to 13A,14A, 15A and 15B.

Other resonator structures in the art are also applicable to thedetector elements described herein. Such resonator structures could beimplemented in certain of the apparatus, detectors, image sensors, andother devices and systems according to principles herein, based inassemblies of one or more detector elements.

Applicable resonator structures according to principles herein areformed from at least two conductive structures separated by a spacing.The conductive structures can have various morphologies. For example,the conductive structures can be configured in a wedge morphology ordisposed in a cross pattern. In an example, the portions of theconductive structures near the spacing can be configured in a wedgemorphology or in a dual prong morphology. In another example, theportions of the first conductive structures in the vicinity of thespacing can be disposed substantially parallel to each other. In anotherexample, the resonator structure can be coupled with a couplingstructure, where a portion of the coupling structure is disposed in thespacing of the resonator structure. In another example, the resonatorstructure can be formed from at least two conductive structures orientedin an antenna arrangement such that they are spaced apart on the surfaceby a spacing. In another example, the resonator structure can be asplit-ring resonator structure. In an example, any resonator structureaccording to principles herein can be disposed in a pixel pattern on asurface of a dielectric or semiconductor to provide the metamaterialstructure.

In an example, a dimension of the resonator structure is less than awavelength of the target electromagnetic radiation. For example, alength of the resonator structures can be less than about 3.0 mm. Inanother example, a lateral dimension of the resonator structure on asurface can be less than about 3.0 In another example, a lateraldimension of the resonator structure on a surface can range from about3.0 μm to about 3.0 mm.

The dimensions of the resonator structures can be configured to be lessthan a wavelength of the target electromagnetic radiation (i.e., rangingfrom about 3.0 μm to about 3.0 mm) such that the metamaterial structureresonates with the target electromagnetic radiation. In an example, thedimensions of each of the conductive structures are configured to beless than a half of the wavelength of the target electromagneticradiation. In an example, the dimensions of each of the conductivestructures are configured to be less than a half of the wavelength ofthe target electromagnetic radiation reduced by a factor that depends onthe effective refractive index of the substrate of the metamaterial. Forexample, for a resonator structure intended to resonate with targetelectromagnetic radiation of wavelength (λ_(t)), a dimension (l) ofconductive structures of the resonator structure can be determinedaccording to the expression: l<λ_(t)/2·n_(eff), where n_(eff) representsthe effective refractive index of the substrate material.

In some non-limiting examples, the dimensions of the resonatorstructures can be configured to be greater than or approximately equalto a wavelength of the target electromagnetic radiation (i.e., rangingfrom about 3.0 μm to about 3.0 mm) such that the target electromagneticradiation resonates with higher order modes of the resonator structure.

In an example, the spacing can be about 1.0 microns (μm). In anotherexample, the spacing can be less than about 1.0 microns, or greater thanabout 1.0 microns. The size of the spacing can be varied (i.e., tuned)to tune the amount of the electric field enhancement. For example, anarrower spacing (e.g., less than about 1.0 microns) can produce largerelectric field enhancement. In another example, a wider spacing (e.g.,greater less than about 1.0 microns) can be used to prevent potentialdamage of the substrate near the spacing (e.g., due to dielectricbreakdown for a dielectric substrate).

In various examples, the portions of an apparatus, detector, imagesensor, or other device or system that includes the detector elementsdescribed herein can be maintained at atmospheric pressure or at lessthan atmospheric pressure, including near vacuum pressures. In anexample, the portions of an apparatus, detector, image sensor, or otherdevice or system that includes the detector elements described hereincan be hermetically sealed.

The operation of the detector elements herein exploits an electric fieldenhancement in the substrate in the region of the spacing when theresonator structure is exposed to electromagnetic radiation at afrequency in the detection range. According to a principle herein, thesubstrate is formed from a material or a device that produces aphoto-induced conductivity response as a result of the electric fieldenhancement. In a non-limiting example, the substrate is a material thatcan undergo a transition to a more conductive state in the presence of asufficiently high electric field. In an example metamaterial structurewith a dielectric substrate, the photo-induced conductivity response canbe based on an insulator-to-metal phase transition in the dielectriccaused by the local electric field enhancement in the region of thespacing (and/or in some examples, a gap) in the resonator structure whenthe detector is exposed to the target electromagnetic radiation. Themetal-insulator transition near the spacing is accompanied by largeresistivity changes, of several orders of magnitude, which can bedetected (including being quantified) according to a system, method orapparatus herein. In an example metamaterial structure with asemiconductor substrate, the photo-induced conductivity response can bebased on impact ionization. In impact ionization, absorption of theincident electromagnetic radiation generates charge carriers which, inthe local high electric field enhancement near the spacing, can generatemultiple additional charge carriers in the substrate through avalanchemultiplication (similar to avalanche photo-diodes). This change incharge carriers can be detected (including being quantified) accordingto a system, method or apparatus herein.

Non-limiting examples of dielectric materials applicable to the variousdetector elements described herein include dielectric materials based onsilicon, germanium, or transition metals. Non-limiting examples of suchtransition metal dielectrics include oxides, phosphate, or silicates ofTi, V, Cr, Mn, Fe, Co, Ni, Cu, Ru, Hf, Ta, or Zr, or any combinationthereof. For example, the dielectric material can be an oxide ofvanadium, such as VO₂ or (V_(1-x)Ti_(x))₂O₃.

Non-limiting examples of semiconductor materials applicable to thevarious detector elements described herein include silicon, germanium,and III-V semiconductors. Non-limiting examples of applicable III-Vsemiconductors include gallium arsenide, indium arsenide, indium galliumarsenide, indium phosphide and indium antimonide.

In an example, an apparatus, detector, image sensor, or other device orsystem that includes detector elements according to the principlesherein can be operated at or near room temperature. In another example,an apparatus, detector, image sensor, or other device or system thatincludes detector elements according to the principles herein can beoperated at temperatures higher than about 77K (liquid nitrogen, LN). Atthese higher than LN temperatures, the detector elements according tothe principles herein can be operated to detect or otherwise quantifyelectromagnetic radiation even at lower light levels where thermalcarriers may act to reduce the signal. A metamaterial that includes asubstrate comprised of a small bandgap material may be operatedaccording to an example implementation herein at temperatures higherthan LN. For example, the bandgap of a III-V semiconductor substratethat includes indium or gallium can be tuned by varying the proportionof indium and/or gallium in the material. In an example, an exampleapparatus, detector, image sensor, or other device or system herein caninclude one or more of the detector elements that are associated with athermoelectric material or thermoelectric device. When supplied with avoltage or current, the a thermoelectric material or thermoelectricdevice can be used to cool the one or more detector elements for moreoptimal operation and conductivity measurement.

The thickness of the substrate can range from between about 50 nm andabout 10 microns in thickness. In other examples, the thickness of thesubstrate can be greater than about 10 microns or less than about 50 nm.In an example, the thickness of the substrate can be up to about 250 nm.

The conductive structures in any example herein can be formed from aconductive metal, a conductive metal oxide, or other conductivematerial. In an example, a conductive structure herein can be based ongold, platinum copper, tantalum, tin, tungsten, titanium, tungsten,cobalt, chromium, silver, nickel or aluminum, or a binary or ternarysystem of any of these conductive materials. The thickness of theconductive structures on the substrate surface can range between about 2nm and about 250 nm in thickness. In other examples, the thickness ofthe conductive structures can be greater than about 250 nm or less thanabout 2 nm. In an example, the thickness of the conductive structurescan be about 200 nm. As a non-limiting example, the conductivestructures can be a gold/chromium system, formed from about 200 nmthickness of gold over a 20 nm thick chromium adhesion layer.

In some examples, a detector element herein can include electrodes thatare in electrical communication (or otherwise electrically coupled) toone or more of the resonator structures of that detector element. Theseelectrodes can be formed from a conductive metal, a conductive metaloxide, or other conductive material, as described above in connectionwith the conductive structures. The thickness of the electrodes canrange between about 7 nm and about 100 nm in thickness, or be greaterthan about 100 nm.

As described above, the change in conductivity of the detector elementcan be measured using electrodes in electrical communication with (orotherwise electrically coupled to) at least one of the resonatorstructures, or using readout circuitry associated with the detectorelement. The measured conductivity in the presence of the targetelectromagnetic radiation can be compared to the measured conductivityin the absence of the target electromagnetic radiation. A change in themeasured conductivity can be indicative of the presence of the targetelectromagnetic radiation, or otherwise quantify a property of thetarget electromagnetic radiation (including magnitude, spatial profile,polarization, etc.).

In an example, the change in conductivity can be measured based on avoltage measurement and/or a current measurement.

According to a system, apparatus and method herein, the measured degreeof change of photo-induced conductivity can be related to the power ofthe incident electromagnetic radiation at the frequencies in thedetection range.

In an example, the resonator structure can be configured to target aspecific frequency of electromagnetic radiation (or range offrequencies) within the detection range. For example, the length (orother dimension) of the conductive structures can be selected based onthe frequency (or range of frequencies) of the electromagnetic radiationto be detected. In an example, the resonator structures can be of alength that is less than a wavelength of the target electromagneticradiation (i.e., ranging from about 3.0 μm or less to about 3.0 mm ormore). In another example, the resonator structures can be of a lengththat is greater than or approximately equal to a wavelength of thetarget electromagnetic radiation such that the target electromagneticradiation resonates with higher order modes of the resonator structure.The size of the spacing is configured such that the local electric fieldenhancement in the spacing in the presence of the target electromagneticradiation results in the resonator structure resonating with the targetelectromagnetic radiation. In a non-limiting example, the spacing isaround 1.0 microns (μm). In other examples, the spacing can be less thanabout 1.0 microns (μm), or greater than about 1.0 microns (μm).

In another example, detector elements of an example device can bearranged such that they can be independently rotated. For example,vertically polarized electromagnetic radiation can be enhanced atportions of a resonator structure where the conductive structures aboutthe spacing are oriented essentially vertically. If the detector elementis rotated away from that orientation, then the degree of resonancechanges (i.e., diminishes) sharply. As a result, the electric fieldenhancement is much weaker and significantly fewer charge carriers aregenerated. Thus, the conductivity change based on the amount of chargecarriers generated can be measured for different rotation angles ofdetector elements relative to the target electromagnetic radiation. Themeasured conductivity change can provide an indication of the degree ofresonance between the detector element and the target electromagneticradiation, and thereby provide a measure of the polarization of thetarget electromagnetic radiation. In an example implementation, detectorelements can be separately and independently rotated to detect orotherwise quantify the polarization direction of the targetelectromagnetic radiation.

In an example, the resonator structure can be configured to targetelectromagnetic radiation at a specific polarization (or range ofpolarizations). As previously mentioned, vertically polarizedelectromagnetic radiation can be enhanced at portions of a resonatorstructure where the conductive structures about the spacing are orientedessentially vertically. Conductive structure portions of the resonatorstructure about the spacing that are not oriented substantiallyvertically, e.g., that are curved or oriented at an angle, may notresonate with that vertically polarized electromagnetic radiation.Rather, these conductive structure portions may be oriented so that theyresonate with electromagnetic radiation with a polarization that is awayfrom the vertical but that is roughly parallel to their direction. Basedon this principle, detector elements can be configured for detecting orotherwise quantifying electromagnetic radiation of differentpolarization directions. That is, the resonator structures of theseexample detector elements can be configured such that the conductivestructure portions neighboring the spacing are oriented at differingangles. In an example according to this principle, an array of detectorelements that include resonator structures with differing angularconfigurations about their respective spacing(s) can be used to detector otherwise quantify electromagnetic radiation at differentpolarizations. In an example according to this principle, the array ofdetector elements can be spatially arranged such that differing regionsof the array resonate with electromagnetic radiation of differingpolarizations.

In another example, detector elements or sensor elements can be arrangedsuch that they can be independently rotated for calibrating a device orfor measurement of the properties of the target electromagneticradiation. For example, for detector elements that are based onsplit-ring resonator structures, a non-linear dependence of the degreeof resonance of the resonator structure can be observed. For example,for a detector element based on the SRR in FIG. 15A-B that is rotated inthe presence of target electromagnetic radiation, the degree of electricfield enhancement (and as a result, the amount of induced chargecarriers) can be observed to differ for each 90° rotation. Such adifferent in resonance response can be due to differences in theconductive structures that bracket a spacing, differences in the sizesof spacings, and differences in the homogeneity of the substratematerial in the neighborhood of a spacing. Any resonator structuresaccording to principles herein can show similar non-symmetrical,non-linear electric field enhancement behavior with rotation. Suchdifferences in resonance response can be calibrated for a given detectorelement or sensor element. In an example operation, such differences inresonance response can be used for normalizing measurements of thetarget electromagnetic radiation made using the detector element orsensor element. In another example, the differences in resonanceresponse can be exploited for providing a measure of the presence of thetarget electromagnetic radiation or otherwise quantify a property of thetarget electromagnetic radiation (including magnitude, spatial profile,polarization, etc.), as described herein.

In another example, the detector elements or sensor elements can beformed metamaterials that have varying substrate properties, and hencevarying resonances. As described above, for a resonator structureintended to resonate with target electromagnetic radiation of wavelength(λ_(t)), a dimension (l) of conductive structures of the resonatorstructure can be determined according to the expression:l<λ_(t)/2·n_(eff), where n_(eff) is the effective refractive index ofthe substrate material. Accordingly, for a given resonator structurewith specified dimensions, the wavelength of electromagnetic radiationthat resonates with it can differ depending on the effective refractiveindex of the substrate in the region of that resonator structure. In anexample implementation, an apparatus, detector, image sensor, or otherdevice or system that includes detector elements or sensor elementsaccording to the principles herein can be configured to detect ofotherwise quantify target electromagnetic radiation of differingfrequencies at different spatially-specific positions on a device arrayby modulating the effective refractive index of the substrate materialof specific detector elements or sensor elements at specified positionsof the device array.

Non-Limiting Examples of Detector Elements and Sensor Elements

An example detector element 200 is illustrated in FIG. 2A. The detectorelement includes a substrate 212 and a resonator structure 214 disposedon the surface of substrate 212. The substrate 212 can be formed from adielectric or semiconductor material, as described above. In theillustration of FIG. 2A, the surface is taken to lie in a y-z plane. Theresonator structure 214 is formed from conductive structures (214 a, 214b, 214 c, and 214 d) that are aligned in a substantially rectangulararrangement. The conductive structures (214 a, 214 b, 214 c, and 214 d)can be formed from a conductive metal, a conductive metal oxide, orother conductive material, as described above. Adjacent ends ofconductive structures are spaced apart by a spacing 215. A magnifiedview of region A is shown in FIG. 2B. As shown in FIG. 2B, the spacing215 separates portions of conductive structures 214 a and 214 b andconductive structures 216 a and 216 b. As described above, in thepresence of target electromagnetic radiation (i.e., at a frequencywithin the detection range), there is a resonant response of theresonator structure. Charge carriers are generated in a region of thesubstrate near the spacing 215 based on an enhanced electric fieldinduced in the spacing 215. The change in conductivity based on theseinduced charge carriers can be measured (i.e., quantified) to indicatethe presence of the target electromagnetic radiation. In an example, theconductivity measurement also can be used to quantify a magnitude of theincident electromagnetic radiation.

An apparatus that includes the resonator structure 214 shown in FIGS. 2Aand 2B also can be implemented to detect target electromagneticradiation at a more than a single polarization. As shown in FIG. 2B, theresonator structure 214 is configured in a cross morphology with spacing215 in between the conductive structures that form the cross.Electromagnetic radiation that is vertically polarized (i.e., along thez-axis in FIG. 2A) can generate the local electric field enhancement inthe spacing 215 through resonantly coupling to the conductive structuresabout the spacing 215 that also are oriented along the z-axis.Electromagnetic radiation that is horizontally polarized (i.e., alongthe z-axis in FIG. 2A) can generate the local electric field enhancementin the spacing 215 through resonantly coupling to the conductivestructures about the spacing 215 that also are oriented along they-axis. In an example implementation, the change in conductivity basedon the induced charge carriers can be measured to indicate the presenceof vertically or horizontally polarized target electromagneticradiation, or otherwise quantify a property of the targetelectromagnetic radiation (including magnitude, spatial profile, etc.)as a function of the polarization direction.

In the non-limiting example of FIG. 2B, portions of conductivestructures 214 a and 216 b neighboring one of the spacings 215 areconfigured with a dual prong morphology. Such a morphology canfacilitate more isotropic local electric field enhancement in thespacing 215. FIG. 2B illustrates example electric field lines 220 thatcan be induced between the conductive structures when the resonatorstructure 214 resonates with incident electromagnetic radiation having arange of different polarizations. Based on the dual prong morphology ofthe conductive structures, the local electric field enhancement can bemore uniform at each of the four spacings 215 about the resonatorstructure 214, which can facilitate better detection of the inducedcharge carriers. The change in conductivity based on the induced chargecarriers due to the different polarizations can be measured to indicatethe presence of the target electromagnetic radiation and itspolarization. The conductivity measurement also can be used to quantifya property of the target electromagnetic radiation (including magnitude,spatial profile, etc.) as a function of the polarization direction.

In an example, the resonator structure 214 can be configured to target aspecific frequency of electromagnetic radiation (or range offrequencies) within the detection range. For example, the length ofconductive structures (214 a, 214 b, 214 c, and 214 d) can be selectedbased on the frequency (or range of frequencies) of the electromagneticradiation to be detected, according to the principles described herein.In an example, the resonator structure 214 can be of a length that isless than a wavelength of the target electromagnetic radiation (i.e.,ranging from about 3.0 μm or less to about 3.0 mm or more). In anotherexample, the resonator structure 214 can be of a length that is greaterthan or approximately equal to a wavelength of the targetelectromagnetic radiation such that the target electromagnetic radiationresonates with higher order modes of the resonator structure. The sizeof the spacing 215 is configured such that the local electric fieldenhancement in the spacing 215 in the presence of the targetelectromagnetic radiation results in the resonator structure 214resonating with the target electromagnetic radiation. In an example, thespacing 215 is around 1.0 microns (μm). In other examples, the spacing215 can be less than about, or greater than about 1.0 microns (μm).

In an example apparatus, detector, image sensor or other device that isformed from a plurality of the resonator structures 214 of FIG. 2A, theresonator structures that are targeted to detect different frequenciesof the target electromagnetic radiation (based on dimensions of theconductive structures) can be disposed at differing spatial locations.An apparatus, detector, image sensor or other device according to suchan example implementation could be used to quantify a property of thetarget electromagnetic radiation (including magnitude, spatial profile,etc.) as a function of the polarization direction.

In an example operation, the detector element 200 is exposed to a beamof electromagnetic radiation that may include the target electromagneticradiation having a frequency (or range of frequencies) within thedetection range. In the presence of the target electromagneticradiation, the local electric field enhancement in the region of thespacing 215 of the resonator structure 214 results in a change of thephoto-induced conductivity of the substrate 212. The change inconductivity of the substrate 212 can be measured using electrodes inelectrical communication with (or otherwise electrically coupled to) atleast one of the resonator structures, or using readout circuitryassociated with the detector element. The measured conductivity in thepresence of the target electromagnetic radiation can be compared to themeasured conductivity in the absence of the target electromagneticradiation. A change in the measured conductivity can be indicative ofthe presence of the target electromagnetic radiation in the beam ofelectromagnetic radiation.

The change in the measured photo-induced conductivity response of thesubstrate 212 can serve as an indicator of the presence and/or themagnitude of the target electromagnetic radiation in the incident beam.The detector element 200 of FIG. 2A also can be used to provide anindication of the spatial profile of the target electromagneticradiation. In an example, a change in the measured photo-inducedconductivity of the substrate 212 above a pre-determined threshold valuecan serve as an indicator of the presence and/or magnitude of the targetelectromagnetic radiation, or a spatial extent of the targetelectromagnetic radiation. The pre-determined threshold value may bedetermined based on the level of noise of the conductivity measurementsof the substrate or based on a sensitivity limit of the instrument orintegrated circuit used to probe the change in conductivity of thesubstrate.

The detector element of FIG. 2A may include electrodes that areelectrically coupled to the substrate 212 or to the resonatorstructure(s) 214 for measuring the change in conductivity due to thecharge carriers induced in the substrate by the local electric fieldenhancement in the spacing 215. In another example, integrated circuitrycoupled to substrate 212 can be used for measuring the change inconductivity due to the charge carriers induced in the substrate by thelocal electric field enhancement in the spacing 215.

FIG. 3 shows an example of an apparatus 300 that includes multiplesensor elements (302, 304, 306, and 308). Each sensor element (302, 304,306, and 308) includes one or more detector elements. In a non-limitingexample, the detector elements of a sensor element can be arranged in anarray. The detector elements of a sensor element can be any of theexample detector elements described herein, including any of FIGS. 2A,2B, 4-12, 13A, 14A, and 15B, or any combination thereof. In an example,the apparatus 300 can be implemented as part of a detector, an imagesensor or other device, and used to detect the presence of, or otherwisequantify a property of, the target electromagnetic radiation (includingmagnitude, polarization, spatial profile, etc.). As shown in FIG. 3,each sensor element is coupled to contacts, such as the contacts shownat 310. In various examples, the contacts may be coupled to electrodesthat are in electrical communication with (or otherwise electricallycoupled to) at least one of the resonator structures of the detectorelements, or the contacts may be coupled to readout circuitry associatedwith the detector elements. The change in conductivity of the substrateof the detector elements in the presence of the target electromagneticradiation (as described herein) can be measured by way of thesecontacts. The measured conductivity in the presence of the targetelectromagnetic radiation can be compared to the measured conductivityin the absence of the target electromagnetic radiation. A change in themeasured conductivity can be indicative of the presence of, or otherwisequantify a property of, the target electromagnetic radiation (includingmagnitude, polarization, spatial profile, etc.).

Another example detector element 400 is illustrated in FIG. 4. Thedetector element includes a substrate 412 and a resonator structure 414disposed on the surface of substrate 412. The substrate 412 can beformed from a dielectric or semiconductor material, as described above.The resonator structure is formed from conductive structures (414 a and414 b) that each have a wedge morphology. The conductive structures (414a and 414 b) can be formed from a conductive metal, a conductive metaloxide, or other conductive material, as described above. The narrowerportions of conductive structures (414 a and 414 b) are adjacent andspaced apart by a spacing 415. As described above, in the presence oftarget electromagnetic radiation (i.e., at a frequency within thedetection range), there is a resonant response of the resonatorstructure. Charge carriers are generated in a region of the substratenear the spacing 415 based on an enhanced electric field induced in thespacing 415. The change in conductivity based on these induced chargecarriers can be measured (i.e., quantified) to indicate the presence ofthe target electromagnetic radiation. In an example, the conductivitymeasurement also can be used to quantify a magnitude of the incidentelectromagnetic radiation.

An apparatus that includes the detector element shown in FIG. 4 also canbe implemented to detect target electromagnetic radiation having a rangeof different polarizations. Based on the non-linear shape (i.e., theedge is at angle θ relative to the center) of the conductive structures,electromagnetic radiation having a range of different polarizations cancause an enhanced electromagnetic field to be induced in the substrate412 in the vicinity of spacing 415. The change in conductivity based onthe induced charge carriers due to the different polarizations can bemeasured to indicate the presence of the target electromagneticradiation. The conductivity measurement also can be used to quantify amagnitude of the target electromagnetic radiation.

In an example, the size of the angle (θ) of the wedge-shaped conductivestructures and/or their alignment direction in the y-z plane in FIG. 4can be varied (i.e., tuned) so that the resonator structure can be usedto detect or otherwise quantify differing ranges of polarizations of theincident electromagnetic radiation. For example, the verticalorientation (i.e., along the z-axis in FIG. 4) of conductive structures41 a and 414 b facilitates enhancement of vertically polarizedelectromagnetic radiation. The angular spread of the wedge-shapedportions also facilitates enhancement of electromagnetic radiation thatis polarized within an angular range about the z-axis. For an exampleapparatus, detector, image sensor or other device that is formed fromtwo or more of the resonator structures of FIG. 4, different resonatorstructures that are targeted to detect different specific ranges ofpolarizations of the target electromagnetic radiation can be disposed atdiffering spatial locations. In another example, apparatus, detector,image sensor or other device that is formed from two or more of theresonator structures of FIG. 4, resonator structures that are targetedto detect the same specific ranges of polarizations of the targetelectromagnetic radiation can be disposed at differing spatial locationsbut rotated to differing directions relative to the z-axis shown in FIG.4. An apparatus, detector, image sensor or other device according tothese example implementations also could be used to detect quantify aproperty of the target electromagnetic radiation (including magnitude,spatial profile, etc.) as a function of the polarization directions ofthe incident electromagnetic radiation.

In an example, the resonator structure can be configured to target aspecific frequency of electromagnetic radiation (or range offrequencies) within the detection range. For example, the length 1 ofconductive structures (414 a and 414 b) can be selected based on thefrequency (or range of frequencies) of the electromagnetic radiation tobe detected. For example, the resonator structure can be of a lengththat is less than a wavelength of the target electromagnetic radiation(i.e., ranging from about 3.0 μm or less to about 3.0 mm or more). Inanother example, the resonator structure can be of a length that isgreater than or approximately equal to a wavelength of the targetelectromagnetic radiation such that the target electromagnetic radiationresonates with higher order modes of the resonator structure. The sizeof the spacing 415 can be around 1.0 microns (μm). In other examples,the spacing 415 can be less than about 1.0 microns (μm) or greater thanabout 1.0 microns (μm).

In an example operation, the detector element 400 is exposed to a beamof electromagnetic radiation that may include the target electromagneticradiation having a frequency (or range of frequencies) within thedetection range. In the presence of the target electromagneticradiation, the local electric field enhancement in the region of thespacing 415 of the resonator structure results in a change of thephoto-induced conductivity of the substrate 412. The change inconductivity of the substrate 412 can be measured using electrodes inelectrical communication with (or otherwise electrically coupled to) atleast one of the resonator structures, or using readout circuitryassociated with the detector element. The measured conductivity in thepresence of the target electromagnetic radiation can be compared to themeasured conductivity in the absence of the target electromagneticradiation. A change in the measured conductivity can be indicative ofthe presence of the target electromagnetic radiation.

The change in the measured photo-induced conductivity response of thesubstrate 412 can serve as an indicator of the presence and/or themagnitude of the target electromagnetic radiation in the incident beam.Therefore, the detector element 400 of FIG. 4 also can be used toprovide an indication of the spatial profile of the targetelectromagnetic radiation. In an example, a change in the measuredphoto-induced conductivity of the substrate 412 above a pre-determinedthreshold value can serve as an indicator of the presence and/ormagnitude of the target electromagnetic radiation, or a spatial extentof the target electromagnetic radiation. The pre-determined thresholdvalue may be determined based on the level of noise of the conductivitymeasurements of the substrate or based on a sensitivity limit of theinstrument or integrated circuit used to probe the change inconductivity of the substrate.

The detector element of FIG. 4 may include electrodes that areelectrically coupled to the substrate 412 or to the resonatorstructure(s) for measuring the change in conductivity due to the chargecarriers induced in the substrate by the local electric fieldenhancement in the spacing 415. In another example, integrated circuitrycoupled to substrate 412 can be used for measuring the change inconductivity due to the charge carriers induced in the substrate by thelocal electric field enhancement in the spacing 415.

Another example detector element 500 is illustrated in FIG. 5. Thedetector element is includes a substrate 512, a resonator structure 514and a coupling structure 518, both of which are disposed on the surfaceof substrate 512. The substrate 512 can be formed from a dielectric orsemiconductor material, as described above. The resonator structure isformed as a conductive structure 514 that includes a spacing 515. Theconductive structures 514 can be formed from a conductive metal, aconductive metal oxide, or other conductive material, as describedabove. The arrows labeled RS show the dimensions and extent of theresonator structure 514. In an example, a portion of the couplingstructure 518 is disposed in spacing 515 the first resonator structure514. The coupling structure 518 does not make physical contact with theresonator structure 514. As described above, in the presence of targetelectromagnetic radiation (i.e., at a frequency within the detectionrange), there is a resonant response of the resonator structure. Chargecarriers are generated in a region of the substrate near the spacing 515based on an enhanced electric field induced in the region of spacing515. Coupling structure 518 can facilitate near-field coupling so thatthe response of the substrate to the resonant coupling (including theinduced charge carriers) can be read-out over the length of couplingstructure 518. In an example implementation, electrodes can beelectrically coupled to the resonator structure 514 by way of couplingstructure 518 to facilitate read-out of the response of the substrate tothe resonant coupling (including the induced charge carriers). Thechange in conductivity based on these induced charge carriers can bemeasured (i.e., quantified) to indicate the presence of the targetelectromagnetic radiation. In an example, the conductivity measurementalso can be used to quantify a magnitude of the incident electromagneticradiation.

In an example, an apparatus, detector, image sensor or other devicebased on the detector element of FIG. 5 can be used for broadbandelectromagnetic spectrum detection. The resonator structure 514 andcoupling structure 518 can exhibit multiple resonant modes that coupleto electromagnetic radiation in the detection range, allowing for fairlybroad spectrum detection. The resonator structure 514 can be modeled ascapacitor-inductor (LC) resonators. The materials of the conductivestructures and the dimensions of the resonator structures set theparameters L and C, and can be used to model the resonant frequency ofthe metamaterial structure, i.e., the target electromagnetic frequencyor range of frequencies that resonate with the metamaterial structure.

In an example, the dimensions of the resonator structure 514 andcoupling structure 518 can be selected based on the range of frequenciesof the electromagnetic radiation to be detected. For example, theresonator structure can have dimensions that are less than a wavelengthof the target electromagnetic radiation (i.e., ranging from about 3.0 μmor less to about 3.0 mm or more). In another example, the resonatorstructure can have dimensions that are greater than or approximatelyequal to a wavelength of the target electromagnetic radiation such thatthe target electromagnetic radiation resonates with higher order modesof the resonator structure. The size of the spacings 515 and 516 can bearound 5.0 microns (μm). In other examples, the spacings 515 and 516 canbe less than about 5.0 microns (μm) or greater than about 5.0 microns(μm). The dimension of the spacing 515 and 516 puts an upper bound onthe possible lateral dimensions of the coupling structure 518 in theregion of the spacing 515 and 516. The size of gap 519 can be about 1.0microns.

In an example operation, the detector element 500 is exposed to a beamof electromagnetic radiation that may include the target electromagneticradiation having a frequency (or range of frequencies) within thedetection range. In the presence of the target electromagneticradiation, the broadband resonance results in a change of thephoto-induced conductivity of the substrate 512. The change inconductivity of the substrate 512 can be measured using electrodes inelectrical communication with (or otherwise electrically coupled to) atleast one of the resonator structures, or using readout circuitryassociated with the detector element. The measured conductivity in thepresence of the target electromagnetic radiation can be compared to themeasured conductivity in the absence of the target electromagneticradiation. A change in the measured conductivity can be indicative ofthe presence of the target electromagnetic radiation.

In an example implementation, the change in the measured photo-inducedconductivity response of the substrate 512 can serve as an indicator ofthe presence and/or the magnitude of the target electromagneticradiation in the incident beam. Therefore, the detector element 500 ofFIG. 5 also can be used to provide an indication of the spatial profileof the target electromagnetic radiation. In an example, a change in themeasured photo-induced conductivity of the substrate 512 above apre-determined threshold value can serve as an indicator of the presenceand/or magnitude of the target electromagnetic radiation, or a spatialextent of the target electromagnetic radiation. The pre-determinedthreshold value may be determined based on the level of noise of theconductivity measurements of the substrate or based on a sensitivitylimit of the instrument or integrated circuit used to probe the changein conductivity of the substrate.

The detector element of FIG. 5 may include electrodes that areelectrically coupled to the substrate 512 or to the resonatorstructure(s) for measuring the change in conductivity due to the chargecarriers induced in the substrate by the local electric fieldenhancement in the spacing 515. In another example, integrated circuitrycoupled to substrate 512 can be used for measuring the change inconductivity due to the charge carriers induced in the substrate by thelocal electric field enhancement in the spacing 515.

In a non-limiting example implementation, the resonator structure 514can be configured to have dimensions of about 100 microns in length andabout 53 microns in width. The width of the coupling structure 518 inthe region of spacing 515 can be about 5 microns, and gap 519 can bearound 1.0 micron.

FIG. 6 shows an example arrangement of the detector elements of FIG. 5in three arrays 610, 620 and 630. The arrays of FIG. 6 can beimplemented in an apparatus, detector, image sensor or other device thatis used to detect target electromagnetic radiation, i.e., at a frequencyin the detection range. In an example implementation, electrodes can beelectrically coupled to the resonator structures of arrays 610, 620 and630 by way of its associated coupling structure to facilitate read-outof the response of the substrate to the resonant coupling (including theinduced charge carriers) for each array 610, 620 and 630. The structure600 can be configured as a pixel of the an apparatus, detector, imagesensor or other device. In another example, the arrays of FIG. 6 can beused to quantify the magnitude of target electromagnetic radiation.

Another example of a detector element 700 is illustrated in FIG. 7A. Thedetector element includes a substrate 712 and conductive structure 714a, 714 b and 714 c disposed on the surface of substrate 712. Thesubstrate 712 can be formed from a dielectric or semiconductor material,as described above. FIG. 7 also shows a second detector element 702 thatincludes conductive structure 716 a, 716 b and 716 c disposed on thesurface of substrate 712. As shown in FIG. 7B, conductive structures 714a, 714 b and 714 c are a part of resonator structure 714; conductivestructures 716 a, 716 b and 716 c are a part of resonator structure 716.The conductive structures (714 a, 714 b, 714 c, 716 a, 716 b and 716 c)can be formed from a conductive metal, a conductive metal oxide, orother conductive material, as described above. A gap 719 separatesconductive structure 714 a from conductive structure 716 a. A portion ofresonator structure 716 (i.e., conductive structure 716 a) is positionedwithin the spacing in resonator structure 714. The arrows labeled RSshow the dimensions and extent of the resonator structure 714. As shownin FIG. 7B, this portion of resonator structure 716 (i.e., conductivestructure 716 a) serves as a dipole structure relative to the resonatorstructure 714. This dipole structure does not make physical contact withthe resonator structure 714. That is, the structure of FIG. 7B is formedbased on interdigitated resonator structures, where a portion of oneresonator structure is disposed in the spacing of another resonatorstructure and serves as a dipole structure. As described above, in thepresence of target electromagnetic radiation (i.e., at a frequencywithin the detection range), there is a resonant response of theresonator structure. Charge carriers are generated in a region of thesubstrate near the spacing in resonator structure 714 based on anenhanced electric field induced in the region of the spacing. The changein conductivity based on these induced charge carriers can be measured(i.e., quantified) to indicate the presence of the targetelectromagnetic radiation. In an example, the conductivity measurementalso can be used to quantify a magnitude of the incident electromagneticradiation.

In an example, an apparatus, detector, image sensor or other devicebased on the detector elements of FIGS. 7A and 7B also can be used forbroadband electromagnetic spectrum detection. The detector elements 714and 716 of FIGS. 7A and 7B are formed as interdigitated resonatorstructures, where a portion of one resonator structure is disposed inthe spacing of another resonator structure and acts as equivalent dipolestructures. Thus, the structure essentially behaves as a series ofdipoles positioned within the spacings of capacitor-inductor (LC)resonators. In this example, the equivalent dipole structures areoriented in a direction perpendicular to the side of the resonatorstructure neighboring the spacing. In a non-limiting example, forfrequencies above about one or more THz, a surface current may belocalized to the region of the substrate in the vicinity of the dipoles;for lower frequencies, the peak surface current may be largely localizedto the connected portions of the resonator structures. The peak surfacecurrent may be localized to the equivalent dipole structures forfrequencies above about one THz, whereas for frequencies lower thanabout one THz, the peak surface current may be largely localized to theconnected bar (such as conductive structures 714 c and 716 c).

In an example, the dimensions of the resonator structure 714 and dipolestructure 718 can be selected based on the range of frequencies of theelectromagnetic radiation to be detected. For example, the resonatorstructure can have dimensions that are less than a wavelength of thetarget electromagnetic radiation (i.e., ranging from about 3.0 μm orless to about 3.0 mm or more). In another example, the resonatorstructure can have dimensions that are greater than or approximatelyequal to a wavelength of the target electromagnetic radiation such thatthe target electromagnetic radiation resonates with higher order modesof the resonator structure. The dimension of the spacing in a firstresonator structure puts an upper bound on the possible dimensions ofthe equivalent “dipole” portion of a second resonator structure that isdisposed in the spacing. In a non-limiting example, the resonatorstructure can have a length of about 300 microns, and the dimension ofthe equivalent “dipole” portion can be about 35 microns. The gap 719between the equivalent “dipole” portion and the resonator structure inthe spacing can be about one 1.0 micron. In another examples, the gapcan be less than about 1.0 microns (μm) or greater than about 1.0microns (μm).

In an example operation, the detector elements 700 and 702 of FIG. 7Bare exposed to a beam of electromagnetic radiation that may include thetarget electromagnetic radiation having a frequency (or range offrequencies) within the detection range. In the presence of the targetelectromagnetic radiation, the broadband resonance results in a changeof the photo-induced conductivity of the substrate 712. The change inconductivity of the substrate 712 can be measured using electrodes inelectrical communication with (or otherwise electrically coupled to) atleast one of the resonator structures, or using readout circuitryassociated with the detector element. The measured conductivity in thepresence of the target electromagnetic radiation can be compared to themeasured conductivity in the absence of the target electromagneticradiation. A change in the measured conductivity can be used as anindication of the presence of the target electromagnetic radiation.

In an example implementation, the change in the measured photo-inducedconductivity response of the substrate 712 can serve as an indicator ofthe presence and/or the magnitude of the target electromagneticradiation in the incident beam. Therefore, the detector element 700 ofFIG. 7 also can be used to provide an indication of the spatial profileof the target electromagnetic radiation. In an example, a change in themeasured photo-induced conductivity of the substrate 712 above apre-determined threshold value can be used as an indicator of thepresence and/or magnitude of the target electromagnetic radiation, or aspatial extent of the target electromagnetic radiation. Thepre-determined threshold value may be determined based on the level ofnoise of the conductivity measurements of the substrate or based on asensitivity limit of the instrument or integrated circuit used to probethe change in conductivity of the substrate.

The detector element of FIG. 7 may include electrodes that areelectrically coupled to the substrate 712 or to the resonatorstructure(s) for measuring the change in conductivity due to the chargecarriers induced in the substrate by the local electric fieldenhancement in the spacing 715. In another example, integrated circuitrycoupled to substrate 712 can be used for measuring the change inconductivity due to the charge carriers induced in the substrate by thelocal electric field enhancement in the spacing 715.

In a non-limiting example implementation, the resonator structure 714can be configured to have dimensions of about 300 microns in length(e.g., conductive elements 714 b and 716 b), with the equivalent dipolestructure portion having a length of about 53 microns (e.g., conductiveelements 714 a and 716 a). The gap 719 can be around 1.0 micron.

Another example of a detector element 800 is illustrated in FIG. 8. Thedetector element includes a substrate 812 and conductive structure 814a, 814 b, 814 c, 814 d, 816 a, 816 b, 816 c and 816 d disposed on thesurface of substrate 812. The substrate 812 can be formed from adielectric or semiconductor material, as described above. Conductivestructures 814 a, 814 b, 814 c, 814 d, 816 a, 816 b, 816 c and 816 d area part of a resonator structure. The conductive structures (814 a, 814b, 814 c, 814 d, 816 a, 816 b, 816 c and 816 d) can be formed from aconductive metal, a conductive metal oxide, or other conductivematerial, as described above. A spacing 815 separates conductivestructure 814 a from conductive structure 816 a. As described above, inthe presence of target electromagnetic radiation (i.e., having afrequency within the detection range), there is a resonant response ofthe resonator structure. Charge carriers are generated in a region ofthe substrate near the spacing 815 in resonator structure 814 based onan enhanced electric field induced in the region of the spacing 815. Thechange in conductivity based on these induced charge carriers can bemeasured (i.e., quantified) to indicate the presence of the targetelectromagnetic radiation. In an example, the conductivity measurementalso can be used to quantify a magnitude of the incident electromagneticradiation.

In an example, an apparatus, detector, image sensor or other devicebased on the detector element of FIG. 8 also can be used for broadbandelectromagnetic spectrum detection. Most of the resonant response thatproduces the local electric field enhancement that generates the chargecarriers occurs in the region of spacing 815.

In an example, the dimensions of the resonator structure can be selectedbased on the range of frequencies of the electromagnetic radiation to bedetected. For example, the resonator structure can have dimensions thatare less than a wavelength of the target electromagnetic radiation(i.e., ranging from about 3.0 μm or less to about 3.0 mm or more). Inanother example, the resonator structure can have dimensions that aregreater than or approximately equal to a wavelength of the targetelectromagnetic radiation such that the target electromagnetic radiationresonates with higher order modes of the resonator structure.

In an example operation, the detector element 800 of FIG. 8 are exposedto a beam of electromagnetic radiation that may include the targetelectromagnetic radiation having a frequency (or range of frequencies)within the detection range. In the presence of the targetelectromagnetic radiation, the broadband resonance results in a changeof the photo-induced conductivity of the substrate 812. The change inconductivity of the substrate 812 can be measured using electrodes inelectrical communication with (or otherwise electrically coupled to) thecontacts 820 a and 820 b of at least one of the resonator structures, orusing readout circuitry associated with the detector element. Themeasured conductivity in the presence of the target electromagneticradiation can be compared to the measured conductivity in the absence ofthe target electromagnetic radiation. A change in the measuredconductivity can be used as an indication of the presence of the targetelectromagnetic radiation.

In an example implementation, the change in the measured photo-inducedconductivity response of the substrate 812 can serve as an indicator ofthe presence and/or the magnitude of the target electromagneticradiation in the incident beam. Therefore, the detector element 800 ofFIG. 8 also can be used to provide an indication of the spatial profileof the target electromagnetic radiation. In an example, a change in themeasured photo-induced conductivity of the substrate 812 above apre-determined threshold value can be used as an indicator of thepresence and/or magnitude of the target electromagnetic radiation, or aspatial extent of the target electromagnetic radiation. Thepre-determined threshold value may be determined based on the level ofnoise of the conductivity measurements of the substrate or based on asensitivity limit of the instrument or integrated circuit used to probethe change in conductivity of the substrate.

Another example detector element 900 is illustrated in FIG. 9A. Thedetector element includes a substrate 912 and a resonator structure 914disposed on the surface of substrate 912. In the illustration of FIG.9A, the surface is taken to lie in a y-z plane. Resonator structure 914is formed from two conductive structures 914 a and 914 b that arealigned in a longitudinal antenna arrangement. Based on the axes definedin FIG. 9A, the conductive structures 914 a and 914 b are aligned alonga z-direction of the substrate. Adjacent ends of conductive structures914 a and 914 b are spaced apart by a spacing 915 in the z-direction.Electrodes 916 and 918 are in electrical communication with theresonator structure 914. Electrode 916 is depicted as being inelectrical communication with a region of conductive structure 914 a ata position away from the spacing 915. Similarly, electrode 918 isdepicted as being in electrical communication with a region ofconductive structure 914 b at a position away from the spacing 915. Asshown in the non-limiting example of FIG. 9A, electrodes 916 and 918 canbe disposed at or near opposite ends of the substrate 912 in thez-direction and oriented along the y-direction. In an example,electrodes 916 and 918 are disposed on the substrate 912.

In an example, the resonator structure 914 is configured to target aspecific frequency of electromagnetic radiation (or range offrequencies) within the detection range. The length of conductivestructures 914 a and 914 b in resonator structure 914 is selected basedon the frequency (or range of frequencies) of the electromagneticradiation to be detected. In an example, the resonator structure 914 canbe of a length that is less than a wavelength of the targetelectromagnetic radiation (i.e., ranging from about 3.0 μm to about 3.0mm). In another example, the resonator structure 914 can be of a lengththat is greater than or approximately equal to a wavelength of thetarget electromagnetic radiation such that the target electromagneticradiation resonates with higher order modes of the resonator structure.The spacing 915 is selected such that the local electric fieldenhancement in the spacing 915 in the presence of the targetelectromagnetic radiation results in the resonator structure 914resonating with the frequency of that target electromagnetic radiation.In an example, the spacing 915 is around 1.0 microns (μm). The spacing915 can be less than about, or greater than about 1.0 microns (μm).

In an example operation, the detector element 900 is exposed to a beamof electromagnetic radiation that may include the target electromagneticradiation having a frequency (or range of frequencies) within thedetection range. In the presence of the target electromagneticradiation, the local electric field enhancement in the region of thespacing 915 of resonator structure 914 results in a change of thephoto-induced conductivity of the substrate 912. The conductivity of thesubstrate 912 can be measured using electrodes 916 and 918. The measuredconductivity in the presence of the target electromagnetic radiation canbe compared to the measured conductivity in the absence of the targetelectromagnetic radiation. A change in the measured conductivity can beindicative of the presence of the target electromagnetic radiation.

The detector element 910 of FIG. 9A can be used as a detector of thetarget electromagnetic radiation in an incident beam. A change in themeasured photo-induced conductivity response of the substrate 912 canserve as an indicator of the presence in the incident beam of the targetelectromagnetic radiation having a frequency (or range of frequencies)within the detection range. In an example, a change in the measuredphoto-induced conductivity response of the substrate 912 above athreshold value can serve as an indicator of the presence of the targetelectromagnetic radiation. The threshold value for a detector elementmay be determined based on the noise of the conductivity signal measuredusing the electrodes or based on a measurement sensitivity limit of theinstrument probing the change in conductivity at the electrodes.

The detector element 910 of FIG. 9A can be used to provide an indicationof the power of the target electromagnetic radiation in an incidentbeam. For example, the amount of photo-induced conductivity response ofthe substrate 912, as measured using the electrodes 916 and 918 can berelated to the power of the target electromagnetic radiation. In anotherexample, detector element 900 can be used to provide an indication ofthe spatial profile of the target electromagnetic radiation.

In an example, the substrate 912 of detector element 900 of FIG. 9A is adielectric or semiconductor material, as described above. The conductivestructures 914 a and 914 b can be formed from a conductive metal, aconductive metal oxide, or other conductive material, as describedabove. The electrodes 916 and 918 also can be formed from a conductivemetal, a conductive metal oxide, or other conductive material, asdescribed above.

Another example detector element 920 is illustrated in FIG. 9B. Similarto detector element 10 of FIG. 9A, detector element 920 includes asubstrate 922 and a resonator structure 924 disposed on the surface ofsubstrate 922. In the illustration of FIG. 9B, the surface is taken tolie in a y-z plane. Resonator structure 924 is formed from twoconductive structures 924 a and 924 b that are aligned in a longitudinalantenna arrangement. Based on the axes defined in FIG. 9B, theconductive structures 924 a and 924 b are aligned along a z-direction ofthe substrate. Adjacent ends of conductive structures 924 a and 924 bare spaced apart by a spacing 925 in the z-direction. Electrodes 926 and928 are in electrical communication with the resonator structure 924.Electrode 926 is depicted as being in electrical communication with aregion of conductive structure 924 a at a position away from the spacing925. Similarly, electrode 928 is depicted as being in electricalcommunication with a region of conductive structure 924 b at a positionaway from the spacing 925.

In the non-limiting example depicted in FIG. 9B, electrodes 926 and 928are disposed on the substrate 922. As depicted, portions of electrodes926 and 928 can be disposed near opposite ends of the substrate 922 inthe z-direction and oriented in the y-direction, while other portions ofthe electrodes 926 and 928 run substantially parallel to conductivestructures 924 a and 924 b in the z-direction.

The resonator structure 924 is also configured to target a specificfrequency of electromagnetic radiation (or range of frequencies) withinthe detection range. The length of conductive structures 924 a and 924 bin resonator structure 924 is selected based on the frequency (or rangeof frequencies) of the electromagnetic radiation to be detected. In anexample, the resonator structure 924 can be of a length that is lessthan a wavelength of the target electromagnetic radiation (i.e., rangingfrom about 3.0 μm to about 3.0 mm). In another example, the resonatorstructure 924 can be of a length that is greater than or approximatelyequal to a wavelength of the target electromagnetic radiation such thatthe target electromagnetic radiation resonates with higher order modesof the resonator structure. The spacing 925 is selected such that thelocal electric field enhancement in the spacing 925 in the presence ofthe target electromagnetic radiation results in the resonator structure924 resonating with the frequency of that target electromagneticradiation. In an example, the spacing 925 is around 1.0 microns (μm).The spacing 925 can be less than about, or greater than about 1.0microns (μm).

In an example operation, the detector element 920 is exposed to a beamof electromagnetic radiation that may include the target electromagneticradiation having a frequency (or range of frequencies) within thedetection range. In the presence of the target electromagneticradiation, the local electric field enhancement in the region of thespacing 925 of resonator structure 924 results in a change of thephoto-induced conductivity of the substrate 922. The conductivity of thesubstrate 922 in the region of spacing 925 can be measured usingelectrodes 926 and 928. The measured conductivity in the presence of thetarget electromagnetic radiation can be compared to the measuredconductivity in the absence of the target electromagnetic radiation. Achange in the measured conductivity can be indicative of the presence ofthe target electromagnetic radiation.

The detector element 920 of FIG. 9A can be used as a detector of thepresence of the target electromagnetic radiation in an incident beam. Achange in the measured photo-induced conductivity response of thesubstrate 922 can serve as an indicator of the presence in the incidentbeam of the target electromagnetic radiation having a frequency (orrange of frequencies) within the detection range. In an example, achange in the measured photo-induced conductivity response of thesubstrate 922 above a threshold value can serve as an indicator of thepresence of the target electromagnetic radiation. The threshold valuefor a detector element may be determined based on the noise of theconductivity signal measured using the electrodes or based on ameasurement sensitivity limit of the instrument probing the change inconductivity at the electrodes.

Detector element 920 of FIG. 9A also can be used to provide anindication of the power of the target electromagnetic radiation in anincident beam. The amount of photo-induced conductivity response of thesubstrate 922, as measured using the electrodes 926 and 928 can berelated to the power of the target electromagnetic radiation. In anotherexample, detector element 920 can be used to provide an indication ofthe spatial profile of the target electromagnetic radiation.

In an example, the substrate 922 of detector element 920 of FIG. 9B is adielectric or semiconductor material, as described above. The conductivestructures 924 a and 924 b can be formed from a conductive metal, aconductive metal oxide, or other conductive material, as describedabove. The electrodes 926 and 928 can be formed from a conductive metal,a conductive metal oxide, or other conductive material, as describedabove.

Another example detector element 1010 is illustrated in FIG. 10A. Thedetector element includes a substrate 1012 and a resonator structure1014 disposed on the surface of substrate 1012 (where the substratesurface lies in a y-z plane). Resonator structure 1014 is formed fromthree conductive structures 1014 a, 1014 b, and 1014 c that are alignedin a longitudinal antenna arrangement. That is, detector element 1010 issimilar to detector element 900 except that an additional conductivestructure 1014 c is positioned between and spaced apart from the topconductive structure 1014 a and the bottom conductive structure 1014 b.Based on the axes defined in FIG. 9A, the conductive structures 1014 a,1014 b, and 1014 c are aligned along a z-direction of the substrate.Adjacent ends of conductive structures 1014 a, 1014 b, and 1014 c arespaced apart by a spacing 1015 a or 1015 b in the z-direction.Electrodes 1016 and 1018 are in electrical communication with theresonator structure 1014. Electrode 1016 is depicted as being inelectrical communication with a region of conductive structure 1014 a ata position away from the spacing 1015 a. Similarly, electrode 1018 isdepicted as being in electrical communication with a region ofconductive structure 1014 c at a position away from the spacing 1015 b.As shown in the non-limiting example of FIG. 10A, electrodes 1016 and1018 can be disposed at or near opposite ends of the substrate 1012 inthe z-direction and oriented along the y-direction. In the example ofFIG. 10A, electrodes 1016 and 1018 are disposed on the substrate 1012.In another example, electrodes 1016 and 1018 may be disposedsubstantially at the edges of the substrate 1012 (e.g., the edges ofsubstrate 1012 aligned along the y-direction).

In an example, the resonator structure 1014 is configured to target aspecific frequency of electromagnetic radiation (or range offrequencies) within the detection range. The length of conductivestructures 1014 a, 1014 b, and 1014 c in resonator structure 1014 isselected based on the frequency (or range of frequencies) of theelectromagnetic radiation to be detected. In an example, the resonatorstructure 1014 can be of a length that is less than a wavelength of thetarget electromagnetic radiation (i.e., ranging from about 3.0 μm toabout 3.0 mm). In another example, the resonator structure 1014 can beof a length that is greater than or approximately equal to a wavelengthof the target electromagnetic radiation such that the targetelectromagnetic radiation resonates with higher order modes of theresonator structure. Although each conductive structure 1014 a,conductive structure 1014 b, and conductive structure 1014 c isillustrated as having a same length, the lengths may be different. Forexample, conductive structure 1014 a and conductive structure 1014 b mayhave a different length compared to conductive structure 1014 c. Inaddition, the lengths of conductive structure 1014 a and conductivestructure 1014 b may differ from each other. The spacing 1015 a and 1015b are selected such that the local electric field enhancement in thespacings 1015 a, and 1015 b in the presence of the targetelectromagnetic radiation results in the resonator structure 1014resonating with the frequency of that target electromagnetic radiation.In an example, spacings 1015 a, and 1015 b are each around 1.0 microns(μm). Each of the spacings 1015 a, and 1015 b can be less than about, orgreater than about 1.0 microns (μm).

In an example operation, the detector element 1010 is exposed to a beamof electromagnetic radiation that may include the target electromagneticradiation having a frequency (or range of frequencies) within thedetection range. In the presence of the target electromagneticradiation, the local electric field enhancement in the region of thespacings 1015 a, and 1015 b of resonator structure 1014 results in achange of the photo-induced conductivity of the substrate 1012. Theconductivity of the substrate 1012 can be measured using electrodes 1016and 1018. The measured conductivity in the presence of the targetelectromagnetic radiation can be compared to the measured conductivityin the absence of the target electromagnetic radiation. A change in themeasured conductivity can be indicative of the presence of the targetelectromagnetic radiation. Similarly to as described above in connectionwith FIG. 9A, detector element 1010 also can be used to detect thepresence, power, and/or spatial profile of the target electromagneticradiation.

All of the principles described above for the components, materials,features, and operation of detector element 900 of FIG. 9A or detectorelement 920 of FIG. 9B apply to the respective components, materials,features, and operation of detector element 1010.

Yet another example detector element 1040 is illustrated in FIG. 10B.The detector element includes a substrate 1042 and a resonator structure1044 disposed on the surface of substrate 1042 (where the substratesurface lies in a y-z plane). Resonator structure 1044 is formed fromthree conductive structures 1044 a, 1044 b, and 1044 c that are alignedin a longitudinal antenna arrangement. That is, detector element 1040 issimilar to detector element 920 except that an additional conductivestructure 1044 c is positioned between and spaced apart from the topconductive structure 1044 a and the bottom conductive structure 1044 b.Based on the axes defined in FIG. 9B, the conductive structures 1044 a,1044 b, and 1044 c are aligned along a z-direction of the substrate.Adjacent ends of conductive structures 1044 a, 1044 b, and 1044 c arespaced apart by a spacing 1045 a or 1045 b in the z-direction.Electrodes 1046, 1048 are in electrical communication with the resonatorstructure 1044. Electrode 1046 is depicted as being in electricalcommunication with a region of conductive structure 1044 a at a positionaway from the spacing 1045 a. Similarly, electrode 1048 is depicted asbeing in electrical communication with a region of conductive structure1044 c at a position away from the spacing 1045 b.

In the non-limiting example depicted in FIG. 10B, electrodes 1046 and1048 are disposed on the substrate 1042. As depicted, portions ofelectrodes 1046 and 1048 are disposed near opposite ends of thesubstrate 1042 in the z-direction and oriented in the y-direction, whileother portions of the electrodes 1046 and 1048 run substantiallyparallel to conductive structures 1044 a, 1044 b, and 1044 c in thez-direction.

In an example, the resonator structure 1044 is configured to target aspecific frequency of electromagnetic radiation (or range offrequencies) within the detection range. The length of conductivestructures 1044 a, 1044 b, and 1044 c in resonator structure 1044 isselected based on the frequency (or range of frequencies) of theelectromagnetic radiation to be detected. In an example, the resonatorstructure 1044 can be of a length that is less than a wavelength of thetarget electromagnetic radiation (i.e., ranging from about 3.0 μm toabout 3.0 mm). In another example, the resonator structure 1044 can beof a length that is greater than or approximately equal to a wavelengthof the target electromagnetic radiation such that the targetelectromagnetic radiation resonates with higher order modes of theresonator structure. Although each conductive structure 1044 a,conductive structure 1044 b, and conductive structure 1044 c isillustrated as having a same length, the lengths may be different. Forexample, conductive structure 1044 a and conductive structure 1044 b mayhave a different length compared to conductive structure 1044 c. Inaddition, the lengths of conductive structure 1044 a and conductivestructure 1044 b may differ from each other. The spacing 1045 a and 1045b are selected such that the local electric field enhancement in thespacings 1045 a and 1045 b in the presence of the target electromagneticradiation results in the resonator structure 1044 resonating with thefrequency of that target electromagnetic radiation. In an example,spacings 1045 a and 1045 b are each around 1.0 microns (μm). Each of thespacings 1045 a and 1045 b can be less than about, or greater than about1.0 microns (μm).

In an example operation, the detector element 1040 is exposed to a beamof electromagnetic radiation that may include the target electromagneticradiation having a frequency (or range of frequencies) within thedetection range. In the presence of the target electromagneticradiation, the local electric field enhancement in the region of thespacings 1045 a and 1045 b of resonator structure 1044 results in achange of the photo-induced conductivity of the substrate 1042. Theconductivity of the substrate 1042 can be measured using electrodes 1046and 1048. The measured conductivity in the presence of the targetelectromagnetic radiation can be compared to the measured conductivityin the absence of the target electromagnetic radiation. A change in themeasured conductivity can be indicative of the presence of the targetelectromagnetic radiation. Similarly to as described above in connectionwith FIG. 9A or 9B, detector element 1040 also can be used to detect thepresence, power, and/or spatial profile of the target electromagneticradiation.

All of the principles described above for the components, materials,features, and operation of detector element 900 of FIG. 9A or detectorelement 920 of FIG. 9B apply to the respective components, materials,features, and operation of detector element 1040.

In another example, a detector element may be formed substantially asillustrated in FIG. 10A, but include more than one additional conductivestructure positioned between and spaced apart from the top conductivestructure and the bottom conductive structure. Each of the additionalconductive structures positioned is also spaced apart from each of theother additional conductive structures. All of the principles describedabove for the components, materials, features, and operation of detectorelement 900 of FIG. 9A and detector element 1010 of FIG. 10B apply tothe respective components, materials, features, and operation of thisexample detector element.

FIG. 11 illustrates an example where a detector element is formed frommultiple resonator structures. In the non-limiting example of FIG. 11,the example detector element 1100 is formed from three resonatorstructures 1102-i (i=1, 2, and 3), each disposed between and inelectrical communication with respective pairs of electrodes 1104-i and1106-i (i=1, 2, and 3). All of the principles described above for thecomponents, materials, features, and operation of the detector elementsof FIGS. 9A, 9B, 10A and 10B apply to the respective components,materials, features, and operation of this example detector element.

The detector element 1100 is configured to target several differentspecific frequencies (or ranges of frequencies) of electromagneticradiation within the detection range. The three resonator structures1102-i are each of different lengths. As a result, each of the resonatorstructures 1102-i can be configured to target a different specificfrequency (or range of frequencies) of electromagnetic radiation withinthe detection range. That is, the length of resonator structure 1102-1is configured based on a specific frequency (or range of frequencies) ofthe electromagnetic radiation to be detected. As illustrated, the lengthof resonator structure 1102-2 is greater than that of resonatorstructure 1102-1, and as a result resonator structure 1102-2 isconfigured to detect a lower frequency (or a lower range of frequencies)of electromagnetic radiation than that detected using resonatorstructure 1102-1. Although a central value of the range of frequenciesof electromagnetic radiation detected using resonator structure 1102-2is lower than a central value of the range of frequencies ofelectromagnetic radiation detected using resonator structure 1102-1,portions of these ranges of frequencies may overlap. As defined herein,the “central value” of a range of frequencies may be a mean, a mode or amedian frequency of the range of frequencies. As illustrated in FIG. 11,the length of resonator structure 1102-3 is greater than that ofresonator structure 1102-2, and as a result resonator structure 1102-3is configured to detect a lower frequency (or a lower range offrequencies) of electromagnetic radiation than that detected usingresonator structure 1102-2 and 1102-1. Although a central value of therange of frequencies of electromagnetic radiation detected usingresonator structure 1102-3 is lower than a central value of the range offrequencies of electromagnetic radiation detected using resonatorstructure 1102-2, portions of these ranges of frequencies may overlap.

The three resonator structures 1102-i are each of different lengths thatrange from about 3.0 μm to about 3.0 mm. Each of the three resonatorstructures 1102-i is of a length that is less than the wavelength of therespective electromagnetic radiation that it is configured to target.The spacings between the conductive structures of each resonatorstructure 1102-i is selected such that the local electric fieldenhancement in the spacings in the presence of the targetelectromagnetic radiation results in the respective resonator structures1102-i resonating with the frequency of its respective targetelectromagnetic radiation. In an example, the spacings between theconductive structures of resonator structures 1102-i may besubstantially the same. For example, the spacings between the conductivestructures can be around 1.0 μm. In another example, the spacingsbetween the conductive structures of resonator structures 1102-3 may begreater than the spacings between the conductive structures of resonatorstructures 1102-2. In another example, the spacings between theconductive structures of resonator structures 1102-2 may be greater thanthe spacings between the conductive structures of resonator structures1102-1.

Each of the three resonator structures 1102-i is illustrated in FIG. 11as including six conductive structures disposed between the respectiveelectrodes. However, in another example, each of the resonatorstructures 1102-i (i=1, 2, and 3) can include fewer than or more thansix conductive structures disposed between the respective electrodes.The lengths of the conductive structures and the spacings between theseconductive structures for each of the resonator structures 1102-i isconfigured according to the principles described herein so that theresonator structure 1102-i targets a different, specific frequency (orrange of frequencies) of electromagnetic radiation within the detectionrange.

FIG. 12 illustrates other examples of detector elements that are each beformed from multiple resonator structures. In the non-limiting exampleof FIG. 12, each detector element 1200-j (j=1, 2, and 3) is formed fromthree resonator structures disposed between and in electricalcommunication with respective pairs of electrodes. In another example,each detector element 1200-j may be formed from differing numbers ofresonator structures. Detector element 1200-1 is formed from threeresonator structures 1201-i (i=1, 2, and 3) disposed between and inelectrical communication with respective pairs of electrodes 1204-1 and1206-1. Detector element 1200-2 is formed from three resonatorstructures 1202-i (i=1, 2, and 3) disposed between and in electricalcommunication with respective pairs of electrodes 1204-2 and 1206-2.Detector element 1200-3 is formed from three resonator structures 1203-i(i=1, 2, and 3) disposed between and in electrical communication withrespective pairs of electrodes 1204-3 and 1206-3. All of the principlesdescribed above for the components, materials, features, and operationof the detector elements of FIGS. 9A, 9B, 10A and 10B apply to therespective components, materials, features, and operation of thisexample detector element.

The three sets of resonator structures 1201-i, 1202-i, and 1203-i areeach of different lengths. As a result, each of the detector elements1200-j is configured to target a different specific frequency (or rangeof frequencies) of electromagnetic radiation within the detection range.That is, the length of resonator structures 1201-i is configured basedon a specific frequency (or range of frequencies) of the electromagneticradiation to be detected. As illustrated, the length of resonatorstructures 1202-i is greater than that of resonator structures 1201-i,and as a result detector element 1200-2 is configured to detect a lowerfrequency (or a lower range of frequencies) of electromagnetic radiationthan that detected using detector element 1200-1. Although a centralvalue of the range of frequencies of electromagnetic radiation detectedusing resonator structures 1202-i is lower than a central value of therange of frequencies of electromagnetic radiation detected usingresonator structures 1201-i, portions of these ranges of frequencies mayoverlap. As illustrated in FIG. 12, the length of resonator structures1203-i is greater than that of resonator structures 1202-i, and as aresult detector element 1200-3 is configured to detect a lower frequency(or a lower range of frequencies) of electromagnetic radiation than thatdetected using detector elements 1200-2 and 1200-1. Although a centralvalue of the range of frequencies of electromagnetic radiation detectedusing resonator structures 1203-i is lower than a central value of therange of frequencies of electromagnetic radiation detected usingresonator structures 1202-i, portions of these ranges of frequencies mayoverlap.

The three detector elements 1200-j are configured with resonatorstructures 1201-i, 1202-i, and 1203-i of different lengths that rangefrom about 3.0 μm to about 3.0 mm. The resonator structures 1201-i,1202-i, and 1203-i of each detector element 1200-j are of a length thatis less than the wavelength of the respective electromagnetic radiationthat the respective detector element 1200-j is configured to target. Thespacings between the conductive structures of each resonator structure1201-i, 1202-i, and 1203-i is selected such that the local electricfield enhancement in the spacings in the presence of the targetelectromagnetic radiation results in the respective resonator structure1201-i, 1202-i, or 1203-i resonating with the frequency of itsrespective target electromagnetic radiation. In an example, the spacingsbetween the conductive structures of resonator structures 1201-i,1202-i, or 1203-i may be substantially the same. For example, thespacings between the conductive structures can be around 1.0 μm. Inanother example, the spacings between the conductive structures ofresonator structures 1203-i may be greater than the spacings between theconductive structures of resonator structures 1202-i. In anotherexample, the spacings between the conductive structures of resonatorstructures 1202-i may be greater than the spacings between theconductive structures of resonator structures 1201-i.

In the example of FIG. 12, each of the resonator structures 1201-i (i=1,2, and 3), 1202-i (i=1, 2, and 3), and 1203-i (i=1, 2, and 3) includessix conductive structures disposed between the respective electrodes.However, in another example, each of the resonator structures 1201-i(1=1, 2, and 3), 1202-i (1=1, 2, and 3), and 1203-i (i=1, 2, and 3) caninclude fewer than or more than six conductive structures disposedbetween the respective electrodes. The lengths of the conductivestructures and the spacings between the conductive structures for eachof the resonator structures 1201-i (i=1, 2, and 3), 1202-i (i=1, 2, and3), and 1203-i (i=1, 2, and 3) is configured according to the principlesdescribed herein so that the resonator structure 1201-i (1=1, 2, and 3),1202-i (1=1, 2, and 3), and 1203-i (1=1, 2, and 3) targets thedifferent, specific frequency (or range of frequencies) ofelectromagnetic radiation within the detection range.

FIG. 13A illustrates yet another example of a detector element 1300 thatis formed from multiple resonator structures. In the non-limitingexample of FIG. 13A, each resonator structure 1301-i (i=1 and 2), 1302-i(i=1 and 2), 1303-i (i=1 and 2), 1304-i (i=1 and 2), and 1305-i (i=1 and2), and their respective electrodes, are based on a similar form andconformation as the resonator structure 924 and electrodes 926, and 928described in connection with FIG. 9B. Each resonator structure 1301-i(i=1 and 2), 1302-i (i=1 and 2), 1303-i (i=1 and 2), 1304-i (i=1 and 2),and 1305-i (i=1 and 2) of FIG. 13A is formed from a pair of conductivestructures disposed between and in electrical communication withrespective pairs of electrodes. All of the principles described abovefor the components, materials, features, and operation of the detectorelements of FIGS. 9A, 9B, 10A and 10B apply to the respectivecomponents, materials, features, and operation of this example detectorelement.

The five sets of resonator structures 1301-i (1=1 and 2), 1302-i (1=1and 2), 1303-i (1=1 and 2), 1304-i (1=1 and 2), and 1305-i (1=1 and 2)are each of different lengths. As a result, detector element 1300 isconfigured to target several different specific frequencies (or rangesof frequencies) of electromagnetic radiation within the detection range.That is, the length of resonator structures 1301-i (1=1 and 2) isconfigured based on a specific frequency (or range of frequencies) ofthe electromagnetic radiation to be detected. As illustrated, the lengthof resonator structures 1302-i (i=1 and 2) is greater than that ofresonator structures 1301-i (i=1 and 2), and as a result resonatorstructures 1302-i (1=1 and 2) are configured to detect a lower frequency(or a lower range of frequencies) of electromagnetic radiation than thatdetected using resonator structures 1301-i (i=1 and 2). Although acentral value of the range of frequencies of electromagnetic radiationdetected using resonator structures 1302-i (1=1 and 2) is lower than acentral value of the range of frequencies of electromagnetic radiationdetected using resonator structures 1301-i (1=1 and 2), portions ofthese ranges of frequencies may overlap. For similar reasons, resonatorstructures 1303-i (i=1 and 2) is configured to detect a lower frequency(or a lower range of frequencies) of electromagnetic radiation thanresonator structures 1302-i (1=1 and 2), resonator structures 1304-i(i=1 and 2) is configured to detect a lower frequency (or a lower rangeof frequencies) of electromagnetic radiation than resonator structures1303-i (1=1 and 2), and resonator structures 1305-i (i=1 and 2) isconfigured to detect a lower frequency (or a lower range of frequencies)of electromagnetic radiation than resonator structures 1304-i (i=1 and2). Also, although the central values of the range of frequenciesdetected by each of the resonator structures differ, some portion ofthese ranges of frequencies may overlap.

The resonator structures 1301-i (i=1 and 2), 1302-i (i=1 and 2), 1303-i(1=1 and 2), 1304-i (i=1 and 2), and 1305-i (i=1 and 2) are each ofdifferent lengths that range from about 3.0 μm to about 3.0 mm. Thelength of each of resonator structures 1301-i (i=1 and 2), 1302-i (i=1and 2), 1303-i (i=1 and 2), 1304-i (i=1 and 2), and 1305-i (i=1 and 2)is less than the wavelength of the respective electromagnetic radiationthat they are configured to target. The spacings between the conductivestructures of resonator structure 1301-i (i=1 and 2), 1302-i (i=1 and2), 1303-i (i=1 and 2), 1304-i (i=1 and 2), and 1305-i (i=1 and 2) isselected such that the local electric field enhancement in the spacingsin the presence of the target electromagnetic radiation results in therespective resonator structures 1301-i (i=1 and 2), 1302-i (1=1 and 2),1303-i (i=1 and 2), 1304-i (i=1 and 2), or 1305-i (i=1 and 2) resonatingwith the frequency (or range of frequencies) of its respective targetelectromagnetic radiation. In an example, the spacings between theconductive structures of resonator structures 1301-i (i=1 and 2), 1302-i(i=1 and 2), 1303-i (i=1 and 2), 1304-i (i=1 and 2), and 1305-i (i=1 and2) may be substantially the same (around 1.0 μm). In another example,the width of the spacings between the conductive structures of theresonator structures 1301-i (i=1 and 2), 1302-i (i=1 and 2), 1303-i (i=1and 2), 1304-i (i=1 and 2), and 1305-i (i=1 and 2) decreases similarlywith the decrease in their length.

The lengths of the conductive structures and the spacings between theconductive structures for each of the resonator structures 1301-i (1=1and 2), 1302-i (1=1 and 2), 1303-i (i=1 and 2), 1304-i (1=1 and 2), and1305-i (i=1 and 2) are configured according to the principles describedherein so that the resonator structure 1301-i (i=1 and 2), 1302-i (1=1and 2), 1303-i (1=1 and 2), 1304-i (1=1 and 2), and 1305-i (1=1 and 2)targets the different, specific frequency (or range of frequencies) ofelectromagnetic radiation within the detection range.

FIG. 13B illustrates example electromagnetic spectral ranges within thedetection range that the resonator structures of detector element 1300can be configured to detect. In the example of FIG. 13B, resonatorstructures 1301-i (i=1 and 2) are configured to detect electromagneticradiation in the range of frequencies of curve 1351. The resonatorstructures 1302-i (1=1 and 2) are configured to detect electromagneticradiation in the range of frequencies of curve 1352. The resonatorstructures 1303-i (1=1 and 2) are configured to detect electromagneticradiation in the range of frequencies of curve 1353. The resonatorstructures 1304-i (1=1 and 2) are configured to detect electromagneticradiation in the range of frequencies of curve 1354. The resonatorstructures 1305-i (1=1 and 2) are configured to detect electromagneticradiation in the range of frequencies of curve 1355.

FIG. 14A illustrates an example of a detector element 1400 that isformed from multiple resonator structures 1402-i (i=1, 2, 3 . . . n)disposed between and in electrical communication with electrodes 1404and 1406. The resonator structures 1402-i (i=1, 2, 3 . . . n) andelectrodes 1404 and 1406 are disposed on a substrate 1412. All of theprinciples described above for the components, materials, features, andoperation of the detector elements of FIGS. 9A, 9B, 10A and 10B apply tothe respective components, materials, features, and operation of thisexample detector element.

The detector element 1400 is configured as an antenna array (multipleresonator structures 1402-i (1=1, 2, 3 . . . n)) sandwiched betweenelectrodes 1404 and 1406. The array and electrodes are deposited onto asuitable material that exhibits the desired nonlinear response in thepresence of the localized enhanced electric field. The spacings can beabout 1.0 μm to give a large electric field enhancement and the lengthof the conductive structures of the antenna array is configured tointeract with a specific frequency of electromagnetic radiation. Thedetector element works as follows: electromagnetic radiation illuminatesa portion of the detector, the light is absorbed by the antennastructures, enhancing the electric field in the spacings, the enhancedelectric field liberates electrons changing the overall conductivity ofthe substrate, and the change in conductivity is measuredelectronically. In an example, the change in conductivity can bemeasured as a change in voltage across a resistor.

A non-limiting example operation of the detector element of FIG. 14A isshown in FIG. 14B. In panel (1) the detector element 1400 is exposed toa beam of electromagnetic radiation at a THz frequency. In panel (2) theresonator structures 1402-1 (i=1, 2, 3 . . . n) interact with theelectromagnetic radiation to provide an enhanced local electric field inat the spacings. In panel (3) charge carriers (in this example, they areelectrons) are liberated in the substrate 1412 in the spacings by theenhanced electric field, which causes the overall conductivity of thesubstrate 1412 to increase. In panel (4), the relatively long-lastingchange in conductivity (on the order of nanoseconds or longer) can bemeasured via the electrodes 1404 and 1406. In an example, the change inconductivity can be measured using high bandwidth amplifier electronics.

Another example detector element 1500 is illustrated in FIGS. 15A and15B. In FIG. 15B, the detector element 1500 is shown to include asubstrate 1512 and a resonator structure 1514 disposed on the surface ofsubstrate 1512. The substrate 1512 can be formed from a dielectric orsemiconductor material, as described above. The resonator structure 1514is formed from conductive structures patterned in a split-ring resonator(SRR) structure. The conductive structures can be formed from aconductive metal, a conductive metal oxide, or other conductivematerial, as described above. Resonator structure 1514 includes fourspacings formed between conductive structures. For example, resonatorstructure 1514 includes spacing 1515 a (formed between conductivestructures 1514 a and 1514 b) and spacing 1515 b (formed betweenconductive structures 1514 c and 1514 d). In the non-limiting example ofFIG. 15B, each of the spacings (including spacings 1515 a and 1515 b)has a width of about 1.5 microns.

FIG. 15A shows a non-limiting example of a detector region formed froman array of the detector elements 1500 for FIG. 15B. In the non-limitingexample of FIG. 15A, the resonator structures 1514 have a width of about75 microns; the unit cell of each detector element 1500 has width ofabout 100 microns.

As described above, in the presence of target electromagnetic radiation(i.e., at a frequency within the detection range), there is a resonantresponse of the resonator structure. Charge carriers are generated in aregion of the substrate near the spacings based on an enhanced electricfield induced in the spacings. The change in conductivity based on theseinduced charge carriers can be measured (i.e., quantified) to indicatethe presence of the target electromagnetic radiation. In an example, theconductivity measurement also can be used to quantify a magnitude of theincident electromagnetic radiation.

In an example, the resonator structures 1514 can be configured to targeta specific frequency of electromagnetic radiation (or range offrequencies) within the detection range. For example, the length ofresonator structures 1514 can be selected based on the frequency (orrange of frequencies) of the electromagnetic radiation to be detected.In an example, the resonator structure 1514 can be of a length that isless than a wavelength of the target electromagnetic radiation (i.e.,ranging from about 3.0 μm or less to about 3.0 mm or more). In anotherexample, the resonator structure 1514 can be of a length that is greaterthan or approximately equal to a wavelength of the targetelectromagnetic radiation such that the target electromagnetic radiationresonates with higher order modes of the resonator structure. The sizeof the spacings is configured such that the local electric fieldenhancement in the spacings in the presence of the targetelectromagnetic radiation results in the resonator structure 1514resonating with the target electromagnetic radiation. In an example, thespacings (including spacings 1515 a and 1515 b) can be around 1.0microns (μm). In other examples, the spacings (including spacings 1515 aand 1515 b) can be less than about, or greater than about 1.0 microns(μm).

In an example operation, the detector element 1500 is exposed to a beamof electromagnetic radiation that may include the target electromagneticradiation having a frequency (or range of frequencies) within thedetection range. In the presence of the target electromagneticradiation, the local electric field enhancement in the region of thespacings of the resonator structure 1514 results in a change of thephoto-induced conductivity of the substrate 1512. The change inconductivity of the substrate 1512 can be measured using electrodeselectrically coupled to at least one of the resonator structures, orusing readout circuitry associated with the detector element. Themeasured conductivity in the presence of the target electromagneticradiation can be compared to the measured conductivity in the absence ofthe target electromagnetic radiation. A change in the measuredconductivity can be indicative of the presence of the targetelectromagnetic radiation.

The change in the measured photo-induced conductivity response of thesubstrate 1512 can serve as an indicator of the presence and/or themagnitude of the target electromagnetic radiation in the incident beam.The detector element 1500 of FIG. 2A also can be used to provide anindication of the spatial profile of the target electromagneticradiation. In an example, a change in the measured photo-inducedconductivity of the substrate 1512 above a pre-determined thresholdvalue can serve as an indicator of the presence and/or magnitude of thetarget electromagnetic radiation, or a spatial extent of the targetelectromagnetic radiation. The pre-determined threshold value may bedetermined based on the level of noise of the conductivity measurementsof the substrate or based on a sensitivity limit of the instrument orintegrated circuit used to probe the change in conductivity of thesubstrate.

The array of FIG. 15A of the detector elements 1500 of FIG. 15B mayinclude electrodes that are electrically coupled to the substrate 1512or to the resonator structure(s) 1514 for measuring the change inconductivity due to the charge carriers induced in the substrate by thelocal electric field enhancement in the spacings (including spacings1515 a and 1515 b). In another example, integrated circuitry coupled tosubstrate 1512 can be used for measuring the change in conductivity dueto the charge carriers induced in the substrate by the local electricfield enhancement in the spacings (including spacings 1515 a and 1515b).

In another example, a resonator structure in the art can be implementedin detector elements and sensor elements, according to principlesherein. Non-limiting examples of applicable resonator structures includeC-ring SRRs, square SRRs, symmetrical-ring SRRs, omega structureresonators, spiral resonators, multi-spiral resonators, broad-sidecoupled SRRs, broad-side coupled spiral resonators, open SRRs, and opencomplementary SRRs.

As described above, in the presence of target electromagnetic radiation(i.e., at a frequency within the detection range), there can be aresonant response of these resonator structures. Charge carriers cangenerated in a region of the substrate of the resonator structures neara spacing in the structure based on an enhanced electric field inducedin this spacing. The change in conductivity of the substrate can bemeasured using electrodes electrically coupled to at least one of theresonator structures, or using readout circuitry associated with thedetector element. The measured conductivity in the presence of thetarget electromagnetic radiation can be compared to the measuredconductivity in the absence of the target electromagnetic radiation. Thechange in conductivity based on these induced charge carriers can bemeasured (or otherwise quantified) to indicate the presence of thetarget electromagnetic radiation, or a property of the targetelectromagnetic radiation (including magnitude, spatial profile,polarization, etc.), as described above in connection with otherexamples. These resonator structures can be configured to target aspecific frequency of electromagnetic radiation (or range offrequencies) within the detection range by scaling-up or scaling-downthe dimensions, as described above in connection with other examples.

Detectors and Image Sensors

Detector elements that include metamaterial structures according to theprinciples described hereinabove are applicable in CMOS image sensors,CCD image sensors, or any other solid state image sensor technology,including hybrid CCD/CMOS technology. An image sensor that includes adetector element described herein can be implemented in a wide varietyof sensing and imaging applications in a wide range of fields.Non-limiting examples of such fields include consumer electronics,commercial electronics, industrial electronics, aerospace electronics,inspection for security purposes, and medical diagnostics. A CMOS imagesensor or CCD image sensor herein can be configured either as afront-illuminated sensor or a back-illuminated sensor.

Both the front-illuminated image sensor and the back-illuminated imagesensor can be configured as one or more individual sensor elements. Eachsensor element includes circuit elements, at least one detector elementand a substrate. The circuit elements can include readout circuitry. Inan example, the image sensors are formed from an array of the individualsensor elements. The array can be arranged in addressable rows andcolumns. Each sensor element can be constructed with the circuitelements disposed over, and on the same surface of the substrate as, theat least one detector element.

FIG. 16 shows a sensor element 1600 of an example front-illuminatedimage sensor. The sensor element 1600 includes a substrate 1612, one ormore detector elements 1614 disposed over the substrate 1612, andcircuit elements 1618 disposed over the one or more detector elements1614.

FIG. 17A shows a sensor element 1700 of an example back-illuminatedimage sensor. The sensor element 1700 also includes a substrate 1712,one or more detector elements 1714 disposed over the substrate 1712, andcircuit elements 1718 disposed over the one or more detector elements1714. FIG. 17B shows a sensor element 1750 of another exampleback-illuminated image sensor. The sensor element 1750 also includes asubstrate 1752 and circuit elements 1758 disposed over the front surfaceof substrate 1752. The one or more detector elements 1754 are disposedon the opposite surface of the substrate 1752. Sensor element 1750 mayinclude other components 1756 on the front surface of substrate 1752.

In an example, the total thickness of the layers of circuit element1618, 1718 or 1758 can be about 5 or 6 microns or more.

In an example, the substrate of detector element 1614, detector element1714 or detector element 1754 can be formed from a different materialfrom the respective substrate 1612, substrate 1712 or substrate 1752.That is, detector element 1614, detector element 1714 or detectorelement 1754 can be formed from resonator structures disposed on theirown dielectric or semiconductor substrate (as described above), which isthen disposed on substrate 1612, substrate 1712 or substrate 1752,respectively, during fabrication. In such an example implementation, thesensor element 1600, 1700 or 1750 is configured such that there islittle loss of charge carriers from the substrate of detector element1614, 1714 or 1754 to substrate 1612, 1712 or 1752, respectively. Inanother example, detector element 1614, detector element 1714 and/ordetector element 1754 can be formed from resonator structures disposedon a portion of substrate 1612, substrate 1712 or substrate 1752,respectively. In this example, that portion of substrate 1612, substrate1712 or substrate 1752 is configured to be dielectric or semiconductingaccording to the desired properties of the resulting detector element(as described above). As non-limiting examples, resonator structures canbe disposed on a portion of a silicon, GaAs, InGaAs, InAs, InP, or InSbsensor substrate, or other applicable sensor substrate, to providedetector element 1614, detector element 1714 or detector element 1754.The resonator structures can be disposed on a coating on suchsubstrates, such as an anti-reflective coating. In any of theseexamples, the sensor element is configured such that the change inconductivity due to the induced charge carriers can be measured (orotherwise quantified) to indicate the presence of the targetelectromagnetic radiation, or a property of the target electromagneticradiation (including magnitude, spatial profile, polarization, etc.), asdescribed herein.

In an example, the circuit elements 1618, 1718 or 1758 of each sensorelement includes three or four transistors that can be used to convertthe generated charge carriers to a voltage signal to provide the outputof the sensor element. For example, the circuit elements 1618, 1718 or1758 can have a 3-T configuration that includes a reset transistor, asource-follower amplifier, and a sensor element select transistor. Inanother example, the circuit elements 1618, 1718 or 1758 can have a 4-Tconfiguration that includes a transfer gate, a reset transistor, asource-follower amplifier, and a sensor element select transistor. Inother examples, the circuit elements 1618, 1718 or 1758 may include atleast one of a reset transistor, a charge transfer switch transistor, asource-follower amplifier, and/or a sensor element select transistor.

As shown in FIG. 16, a front-illuminated image sensor is configured suchthat it collects light that impinges on the front face of the sensorelement, i.e., at the substrate surface that includes the circuitelements 1618 disposed over the one or more detector elements 1614. Aback-illuminated image sensor, shown in FIG. 17A-B, is configured tocollect electromagnetic radiation that impinges on the back face of thesensor element, i.e., at the opposite substrate surface. By thinning thesubstrate of the back-illuminated image sensor during the manufacturingprocess, light can penetrate through to the detector without passingthrough, or being reflected by, the circuit elements. For an exampleback-thinned sensor herein, the substrate can be thinned to a fewmicrons in thickness, for example about 10 microns, about 6 microns,about 4 microns, or thinner. In another example, the substrate can bethinned to a tens of microns in thickness, for example about 20 microns,about 40 microns, about 70 microns, or thicker.

A front-illuminated imager sensor can be more cost effective tomanufacture than back-illuminated imager sensors. However, a potentialperformance limitation of front-illuminated imager sensor can be a lowerfill factor or lower sensitivity. For example, fill factor can be lessthan about 30%, which means that fewer than 30% of the light energyreceived by the sensor element is detected by the one or more detectorsin the sensor element. The lower fill factor/lower sensitivity can bedue to shadowing caused by the presence of opaque metal bus lines,absorption of light by portions of the circuit elements formed on thefront surface in the detector element regions of the front-illuminatedimage sensor, and/or reflection of light at one or more of theinterfaces between the adjacent dielectric layers formed in the CMOSfabrication process. The light transmission loss at the interfaces isproportional to the number of layers and the thickness of the layers. Aback-illuminated semiconductor imaging sensor can pose some advantagesover a front-illuminated image sensor, including a higher fill factor,potentially better overall efficiency of charge carrier generation andcollection, and potentially better suitability for small pixel arrays.

A back-thinned sensor, formed from a back-illuminated imager sensor mayexhibit loss of charge carriers near the back surface due to danglingbonds present at the silicon back surface. The dangling bonds couldreduce quantum efficiency if the backside of the back-thinned imagesensor element is not treated to reduce, if not remove, the danglingbonds. In back-illuminated imager sensors, photon radiation that entersthe backside of the imager sensor generates charge carriers at or nearthe detector elements as described herein. The location of the chargegeneration about the detector elements depends on the absorption lengthof the incident photon, which in turn depends on its wavelength. Photonswith longer wavelengths (i.e., light closer to the 300 GHz frequencyrange) penetrate deeper into the detector elements layer as compared tothe shorter wavelengths (i.e., light closer to the 10 THz frequencyrange). A depletion layer can be included in the substrate to increasethe efficiency of collection of the charge carriers. The depletion layercan be positioned such that charge carriers generated near the back sideof the image sensor are collected efficiently. This also avoidshorizontal drift of carriers into adjacent sensor elements, which maysmear an image.

FIGS. 18A-D illustrates a schematic of absorption in a semiconductordevice. For a conventional semiconductor-based optoelectronic device,incident electromagnetic radiation may travel a certain distance intothe detector material before being absorbed, which then creates anelectron-hole pair. As shown in FIG. 18A, longer wavelengthelectromagnetic radiation 1802 can penetrate farther into a materialthan shorter wavelength electromagnetic radiation 1804. For a devicethat includes a P-N junction (a depletion region) in the substrate,electron-hole generation should occurs in the depletion region in orderfor the charges to be properly separated. For a device having a thickersubstrate (shown in FIG. 18B), electron-hole pairs generated by thelonger wavelength electromagnetic radiation near the depletion region1808 in the substrate can be collected for detection; electron-holepairs generated with shorter wavelength electromagnetic radiation awayfrom the depletion region recombine before they can be collected.

The substrate of a back-illuminated device is thinned such that shorterwavelength photons, which generate electron-hole pairs near the surface,can be detected since the thinned material results in electron-hole pairgeneration in the depletion region of the device. As shown in FIG. 18C,a back-thinned device can be optimized for collection of electron-holepairs from shorter wavelength light. Such a device can be more sensitiveto shorter wavelength electromagnetic radiation, since the electron-holepairs generated by absorption of shorter wavelength electromagneticradiation are in the depletion region of the device. Since the device isilluminated on the backside, there are no electrodes or circuitry thatcan block the one or more detector elements, so the electromagneticradiation is more efficiently absorbed.

FIG. 18D shows a sensor element 1810 that is comprised of metamaterialstructures according to the principles herein. This exampleimplementation can provide a back-thinned, back-illuminated sensordevice that is sensitive to much longer wavelengths of electromagneticradiation since the concentration of the enhanced electric field in thespacings liberates electrons near the surface of the substrate. Sincethe back-illuminated device is thin and the depletion region is near thesurface, electron-hole pairs can be collected efficiently. A measure ofthe change in conductivity based on the generated electron-hole pairscan be sued to provide an indication of the presence of the targetelectromagnetic radiation, or otherwise quantify a property of thetarget electromagnetic radiation (including magnitude, spatial profile,polarization, etc.). In a non-limiting example, these sensor elementscan be included in an image sensor, such as but not limited to a camera.

In an example, an image sensor herein is fabricate in at least atwo-step process. The detector elements can be fabricated by depositionof the conductive structures described herein on a dielectric orsemiconductor substrate according to at least one configurationdescribed herein. The circuit elements can be formed separatelyaccording to any applicable integrated circuitry fabrication process.The circuit elements can be formed using any conductive material,including copper, tantalum, tin, gold, tungsten, titanium, tungsten,titanium nitride, titanium tungsten, nickel, cobalt, chromium, silver,aluminum, or any combination of two or more of these conductivematerials.

An image sensor herein, whether formed as a front-illuminated imagesensor or the back-illuminated image sensor, can be configured as anarray of individual sensor elements, each of which includes a substrate,at least one detector element, and circuit elements.

An image sensor herein can include one or more arrays of sensorelements. For example, as shown in FIG. 19, an image sensor can beformed from one or more sensor regions 1900, each sensor regionincluding an array of sensor elements 1902. Each sensor element 1902 caninclude one or more detector elements, or a plurality of detectorelements. FIG. 19 shows a non-limiting example of an arrangement ofdetector elements 1906 that are included in a sensor element. The imagesensor may also include regions 1904 that do not include sensorelements. In an example implementation, sensor elements 1902 can beformed as pixels of an image sensor.

FIG. 20 is a block diagram showing the components of a non-limitingexample of an image sensor. The image sensor is a complementarymetal-oxide-semiconductor (CMOS) image sensor 2001 that includes a pixelarray 2000. The pixel array 2000 can be formed from an array of any ofthe image sensors described herein. In an example, the pixel array 2000is formed with pixel cells arranged in a predetermined number of columnsand rows, where a pixel cell includes a sensor element according to anyof the examples herein. The pixel array 2000 can be used to captureincident radiation from an optical image and convert the capturedradiation to electrical signals, such as analog signals.

The electrical signals obtained and generated by the pixel cells in thepixel array 2000 can be read out, row by row, to provide image data ofthe captured optical image. For example, pixel cells in a row of thepixel array 2000 are all selected for read-out at the same time by a rowselect line, and each pixel cell in a selected column of the rowprovides a signal representative of received light to a column outputline. That is, each column also has a select line, and the pixel cellsof each column are selectively read out onto output lines in response tothe column select lines. The row select lines in the pixel array 2000are selectively activated by a row driver 2025 in response to a rowaddress decoder 2027. The column select lines are selectively activatedby a column driver 2029 in response to a column address decoder 2031.

The image sensor 2001 can also include a timing and controlling circuit2033 that generates one or more read-out control signals to control theoperation of the various components in the image sensor 2001. Forexample, the timing and controlling circuit 2033 can control the addressdecoders 2027 and 2031 in any of various conventional ways to select theappropriate row and column lines for pixel signal read-out.

The electrical signals output from the column output lines typicallyinclude a pixel reset signal (V_(RST)) and a pixel image signal(V_(Photo)) for each image pixel cell in a CMOS image sensor. In anexample of an image pixel array 2000 containing four-transistor CMOSimage pixel cell, the pixel reset signal (V_(RST)) can be obtained froma floating diffusion region when it is reset by a reset signal RSTapplied to a corresponding reset transistor, while the pixel imagesignal (V_(Photo)) is obtained from the floating diffusion region whenphoto-generated charge is transferred to the floating diffusion region.Both the V_(RST) and V_(Photo) signals can be read into a sample andhold circuit (S/H) 2035. Although the image sensor 2001 illustrated is aCMOS image sensor, other types of solid state image sensors, pixelarrays, and readout circuitries may also be used.

FIG. 21 illustrates an example processing system 2101 that includes animage sensor 2001. The image sensor 2001 may be combined with aprocessor, such as a CPU, digital signal processor, or microprocessor,with or without memory storage, on a single integrated circuit or on adifferent chip than the processor. In the example shown in FIG. 21, theprocessing system 2101 includes a central processing unit (CPU) 2160,such as a microprocessor, that communicates with an input/output (I/O)device 2162 over a bus 2164. The processing system 2101 also can includerandom access memory (RAM) 2166 and/or removable memory 2168, such asbut not limited to flash memory, which can communicate with CPU 2160over the bus 2164.

The processing system 2101 can be any of various systems having digitalcircuits that could include the image sensor 2001. As a non-limitingexample, processing system 2101 could include a computer system. In theexample shown in FIG. 21, the processing system 2101 can be included ina camera 2101. Incident electromagnetic radiation (e.g., that entersthrough the camera) impinges on and resonates with one or more detectorelements of the pixel array 2000 (see FIG. 20). The generated chargecarriers can be detected according to any example described herein.

While the example of FIGS. 20 and 21 are described with reference to aCMOS image sensor, the detector elements and sensor elements accordingto principles herein can be implemented in other solid state imagesensor technology, including charge-coupled device (CCD) technology orhybrid CCD/CMOS technology. In an example, the image sensors herein areCCD image sensors.

CCD image sensor devices can differ from CMOS sensor devices in wherethe timing and controlling circuitry as located relative to the sensorelements and the detector elements. As described above, a CMOS imagesensor includes an active pixel array with timing and controllingcircuitry coupled with some or all of the sensor elements. The CMOSimage sensor device can include other circuitry for converting measuredchange in conductivity (as described above) to digital information.Also, a CMOS image sensor device can be cheaper to manufacture, can beimplemented with fewer components, use less power, and/or provide fasterread-out than a CCD image sensor device.

In an example CCD image sensor, the timing and controlling circuitry maynot be located on the same substrate as the sensor elements or thedetector elements but rather can be located elsewhere in the imagingsensor device. The measures of the changes in conductivity (as describedabove) can be sampled one pixel at a time as they are read-out from thepixel array. The CMOS image sensor device can include other circuitryfor converting measured change in conductivity (as described above) todigital information. A CCD image sensor can give essentially the samequality performance as a CMOS image sensor device and is a more maturetechnology.

In another example, the detector elements and sensor elements accordingto principles herein can be implemented in hybrid CCD/CMOS technology.Such hybrid CCD/CMOS technology is expected to exhibit the benefits ofboth CCD image sensors and CMOS image sensors. A hybrid CCD/CMOS imagesensor can be formed from CMOS readout integrated circuitry (ROIC) thatis registered with and bump bonded to CCD image sensor substrates. Inthis example, the CCD image sensors and ROIC are fabricated separatelyand later combined. That is, the sensor elements can be fabricated bybonding circuit elements above the detector elements or the sensorelements to provide the hybrid CCD/CMOS image sensor configuration. Inan example, the bonding can be facilitated using metallic interconnectsthat couple each of a number of circuit elements to each of acorresponding number of detector elements or sensor elements.Non-limiting examples of bonding agent include an oxide of silicon, suchas spin-on glass, and polymers, such as parylene, polyimides,benzocyclobutene, photo-resists, and polymethylsiloxane. In anotherexample, the hybrid CCD/CMOS technology can be formed using CMOSfabrication techniques. That is, the CMOS fabrication techniques areutilized to fabricate CCD-like image sensors, with sensor element andcircuitry configurations having the finer dimensions achievable withCMOS technology.

Other Applications Including Detector Elements and Sensor Elements

The sensor elements and detector elements that include metamaterialstructures according to the principles described hereinabove areapplicable in various other applications.

In an example, a device or system that includes at least one sensorelement or detector element according to principles described herein canbe implemented as an active component or as a passive component. In anexample, the detector elements according to principles herein areimplemented as a passive component of a device or a system. That is, inresonating with the target electromagnetic radiation, the detectorelements exhibit a change in conductivity, i.e., a voltage or current.In another example, the detector elements according to principles hereincan be used in a system that includes an active component, such as butnot limited to a transistor or tunnel diode. For example, the system canbe configured so that the charge carriers generated at or near thespacing in the resonator structure can be injected or otherwise coupledto the active component. The injected or coupled charge carriers can bedetected or otherwise quantified based on its effects in changing anoperation parameter of the active component. The change in operationparameter of the active component can be used to provide an indicationof the presence of the target electromagnetic radiation, or otherwisequantify a property of the target electromagnetic radiation (includingmagnitude, spatial profile, polarization, etc.) For example, ametamaterial structure according to the principles herein can beimplemented in ultra-fast THz or GHz transistors.

In another example, a device or system that includes at least one sensorelement or detector element according to principles described herein canbe implemented as an emitter. of electromagnetic radiation in thegigahertz or terahertz frequency range. Such an emitter may operatesimilarly to an Auston switch or other photo-conductive antenna. In anexample operation of such a device or system, electromagnetic radiationis emitted from accelerated carriers in a semiconductor substrate, suchas but not limited to silicon (Si), gallium arsenide (GaAs) or indiumgallium arsenide (InGaAs). Charge carriers (electrons and holes) can begenerated at the surface of the semiconductor by femtosecond laserpulses with photon energies above the bandgap energy of thesemiconductor substrate. An external bias could be applied to electrodescoupled to the metamaterial structures to separate the charge carriersat the spacings. The higher mobility electrons can be accelerated tocontribute to the electromagnetic emission (e.g., at terahertzfrequencies) in a forward and backward direction away from the plane ofmetamaterials.

In another example, a device or system that includes at least one sensorelement or detector element according to principles described herein canbe implemented in detectors that are tuned to detect specific compoundsor spectroscopic signatures. For example, a device or system thatincludes at least one sensor element or detector element according toprinciples described herein can be implemented to provide informationabout the composition of a potentially hazardous compound. Non-limitingexamples of such compounds include explosives, chemical agents, orbiological agents. An example a device or system including at least onesensor element or detector element according to principles describedherein can be implemented to detect specific spectroscopic signatures ofbiological molecules of interest, including biological agents orpathogens. In non-limiting examples, such spectroscopic signatures canbe due to physical processes, including atomic and molecular transitionsand dynamics of the biological molecules. In a non-limiting example, thedevice or system that includes at least one sensor element or detectorelement according to principles described herein can be to scan shippingcontainers, storage containers, trucking compartments, etc, that aremade of non-conductive materials or sufficiently low conductivitymaterials.

Other non-limiting example applications of an apparatus, detector, imagesensor, or other device or system described herein include in security,military, and industrial applications, academic research, and laserscience. Imaging using a system or apparatus described herein can beenincorporated into security applications and industrial process control.The systems and apparatus described herein can be implemented inspectroscopic applications and military uses as well. Additionalpossible applications of the systems and apparatus described hereininclude ultrafast electro-optic switching driven by an electromagneticfield in the gigahertz and/or terahertz frequency ranges.

In another non-limiting example, an apparatus, detector, image sensor,device or system described herein can be made low-cost and/ordisposable.

CONCLUSION

While various inventive embodiments have been described and illustratedherein, those of ordinary skill in the art will readily envision avariety of other means and/or structures for performing the functionand/or obtaining the results and/or one or more of the advantagesdescribed herein, and each of such variations and/or modifications isdeemed to be within the scope of the inventive embodiments describedherein. More generally, those skilled in the art will readily appreciatethat all parameters, dimensions, materials, and configurations describedherein are meant to be exemplary and that the actual parameters,dimensions, materials, and/or configurations will depend upon thespecific application or applications for which the inventive teachingsis/are used. Those skilled in the art will recognize, or be able toascertain using no more than routine experimentation, many equivalentsto the specific inventive embodiments described herein. It is,therefore, to be understood that the foregoing embodiments are presentedby way of example only and that, within the scope of the appended claimsand equivalents thereto, inventive embodiments may be practicedotherwise than as specifically described and claimed. Inventiveembodiments of the present disclosure are directed to each individualfeature, system, article, material, kit, and/or method described herein.In addition, any combination of two or more such features, systems,articles, materials, kits, and/or methods, if such features, systems,articles, materials, kits, and/or methods are not mutually inconsistent,is included within the inventive scope of the present disclosure.

The above-described embodiments of the invention can be implemented inany of numerous ways. For example, some embodiments may be implementedusing hardware, software or a combination thereof. When any aspect of anembodiment is implemented at least in part in software, the softwarecode can be executed on any suitable processor or collection ofprocessors, whether provided in a single computer or distributed amongmultiple computers.

In this respect, various aspects of the invention may be embodied atleast in part as a computer readable storage medium (or multiplecomputer readable storage media) (e.g., a computer memory, one or morefloppy disks, compact disks, optical disks, magnetic tapes, flashmemories, circuit configurations in Field Programmable Gate Arrays orother semiconductor devices, or other tangible computer storage mediumor non-transitory medium) encoded with one or more programs that, whenexecuted on one or more computers or other processors, perform methodsthat implement the various embodiments of the technology discussedabove. The computer readable medium or media can be transportable, suchthat the program or programs stored thereon can be loaded onto one ormore different computers or other processors to implement variousaspects of the present technology as discussed above.

The terms “program” or “software” are used herein in a generic sense torefer to any type of computer code or set of computer-executableinstructions that can be employed to program a computer or otherprocessor to implement various aspects of the present technology asdiscussed above. Additionally, it should be appreciated that accordingto one aspect of this embodiment, one or more computer programs thatwhen executed perform methods of the present technology need not resideon a single computer or processor, but may be distributed in a modularfashion amongst a number of different computers or processors toimplement various aspects of the present technology.

Computer-executable instructions may be in many forms, such as programmodules, executed by one or more computers or other devices. Generally,program modules include routines, programs, objects, components, datastructures, etc. that perform particular tasks or implement particularabstract data types. Typically the functionality of the program modulesmay be combined or distributed as desired in various embodiments.

Also, the technology described herein may be embodied as a method, ofwhich at least one example has been provided. The acts performed as partof the method may be ordered in any suitable way. Accordingly,embodiments may be constructed in which acts are performed in an orderdifferent than illustrated, which may include performing some actssimultaneously, even though shown as sequential acts in illustrativeembodiments.

All definitions, as defined and used herein, should be understood tocontrol over dictionary definitions, definitions in documentsincorporated by reference, and/or ordinary meanings of the definedterms.

The indefinite articles “a” and “an,” as used herein in thespecification and in the claims, unless clearly indicated to thecontrary, should be understood to mean “at least one.”

The phrase “and/or,” as used herein in the specification and in theclaims, should be understood to mean “either or both” of the elements soconjoined, i.e., elements that are conjunctively present in some casesand disjunctively present in other cases. Multiple elements listed with“and/or” should be construed in the same fashion, i.e., “one or more” ofthe elements so conjoined. Other elements may optionally be presentother than the elements specifically identified by the “and/or” clause,whether related or unrelated to those elements specifically identified.Thus, as a non-limiting example, a reference to “A and/or B”, when usedin conjunction with open-ended language such as “comprising” can refer,in one embodiment, to A only (optionally including elements other thanB); in another embodiment, to B only (optionally including elementsother than A); in yet another embodiment, to both A and B (optionallyincluding other elements); etc.

As used herein in the specification and in the claims, “or” should beunderstood to have the same meaning as “and/or” as defined above. Forexample, when separating items in a list, “or” or “and/or” shall beinterpreted as being inclusive, i.e., the inclusion of at least one, butalso including more than one, of a number or list of elements, and,optionally, additional unlisted items. Only terms clearly indicated tothe contrary, such as “only one of” or “exactly one of,” or, when usedin the claims, “consisting of,” will refer to the inclusion of exactlyone element of a number or list of elements. In general, the term “or”as used herein shall only be interpreted as indicating exclusivealternatives (i.e. “one or the other but not both”) when preceded byterms of exclusivity, such as “either,” “one of,” “only one of,” or“exactly one of” “Consisting essentially of,” when used in the claims,shall have its ordinary meaning as used in the field of patent law.

As used herein in the specification and in the claims, the phrase “atleast one,” in reference to a list of one or more elements, should beunderstood to mean at least one element selected from any one or more ofthe elements in the list of elements, but not necessarily including atleast one of each and every element specifically listed within the listof elements and not excluding any combinations of elements in the listof elements. This definition also allows that elements may optionally bepresent other than the elements specifically identified within the listof elements to which the phrase “at least one” refers, whether relatedor unrelated to those elements specifically identified. Thus, as anon-limiting example, “at least one of A and B” (or, equivalently, “atleast one of A or B,” or, equivalently “at least one of A and/or B”) canrefer, in one embodiment, to at least one, optionally including morethan one, A, with no B present (and optionally including elements otherthan B); in another embodiment, to at least one, optionally includingmore than one, B, with no A present (and optionally including elementsother than A); in yet another embodiment, to at least one, optionallyincluding more than one, A, and at least one, optionally including morethan one, B (and optionally including other elements); etc.

In the claims, as well as in the specification above, all transitionalphrases such as “comprising,” “including,” “carrying,” “having,”“containing,” “involving,” “holding,” “composed of,” and the like are tobe understood to be open-ended, i.e., to mean including but not limitedto. Only the transitional phrases “consisting of” and “consistingessentially of” shall be closed or semi-closed transitional phrases,respectively, as set forth in the United States Patent Office Manual ofPatent Examining Procedures, Section 2111.03.

What is claimed is:
 1. An image sensing method, comprising: A)irradiating a detector element, disposed on a first side of a substratehaving a depletion region, with electromagnetic radiation at leastpartially reflected from an object of interest, the detector elementcomprising a resonator structure defined by two conductive structuresseparated by a spacing; B) in response to A), generating charge carriersnear the spacing and in the depletion region of the substrate, based onan enhanced electric field induced in the spacing by a resonant responseof the resonator structure to at least one frequency component in theelectromagnetic radiation; and C) electronically generating an image ofat least a portion of the object of interest based at least in part onthe generated charge carriers.
 2. The image sensing method of claim 1,wherein C) comprises measuring, via a circuit element disposed on asecond side of the substrate, a change of conductivity induced at leastpartially by the generated charge carriers, wherein the second side ofthe substrate is opposite to the first side of the substrate.